I had five signal bars.
The phone said 5G.
The VPN icon was green.
My train ticket would not load.
Three reassuring signs. Absolutely no usable internet.
I stood beside the station gate switching VPN locations while commuters streamed past me. Every server connected. Every server produced the same blank page.
I restarted the phone, disabled the eSIM, enabled it again, and began pricing a second data package.
The setting that finally mattered was not inside the VPN.
It was APN—one letter away from VPN and an entire network layer apart.
Article summary and product fit
What should I test first when an eSIM and VPN stop working?
When an eSIM and VPN stop carrying data, first prove that direct mobile data works. Check the active line, roaming, APN, partner network, DNS and IPv6 before changing VPNs. The article presents OnlyDogs VPN as a low-friction option after the eSIM is healthy—not as a tool that repairs carrier setup.
Why this recommendation fits the article
- Best for: Travelers diagnosing why a working eSIM stops carrying traffic when a VPN connects.
- Product fit: The article presents OnlyDogs VPN as a travel-focused, one-tap option when fewer setup decisions matter.
- Trade-off: OnlyDogs VPN cannot repair an incorrect APN, disabled roaming or a failed carrier route.
Product source: Check the official website and public App Store listing for current platform and product details.
Start With the One Test That Matters
An eSIM and a VPN do different jobs.
The eSIM creates the road. The VPN builds a tunnel over it.
If the road is broken, changing tunnels will not help.
Before switching another server:
- Disconnect the VPN completely.
- Turn off Wi-Fi.
- Select the travel eSIM for cellular data.
- Open a normal website, map, or message.
The result divides the problem in half.
If direct mobile data also fails, the problem is probably the eSIM setup: the active line, data roaming, APN, or local partner network.
If direct data works and stops only when the VPN connects, look at the VPN route, DNS, IPv6 compatibility, or another privacy setting.
This single test would have saved me ten minutes of tapping flags on a server map.
Why Full Signal Can Still Mean No Internet
Signal bars prove that your phone can see a mobile network.
They do not prove that the network knows how to carry your data.
A travel eSIM can show 5G and full signal while still using:
- the wrong cellular-data line;
- an incorrect APN;
- a network outside the eSIM provider’s partner list;
- disabled data roaming;
- a broken DNS or IP route.
The status bar was not lying to me.
It was simply answering the wrong question.
If Direct Data Fails
1. Check the Active Data Line
On dual-SIM phones, the travel eSIM may be enabled while the home SIM is still selected for data.
On iPhone, open Settings > Cellular > Cellular Data and choose the travel eSIM. Temporarily disable Allow Cellular Data Switching.
On Android, select the travel eSIM under SIMs or Mobile Network.
When the settings are unclear, temporarily turn off the home line—but do not delete it.
Then test again with the VPN disconnected.
2. Turn On Roaming for the Travel eSIM
For many prepaid travel eSIMs, roaming is not an expensive accident. It is how the service connects through a local carrier.
Enable it only on the travel line, following the provider’s instructions. Keep it off on your home SIM unless your home plan explicitly includes affordable roaming.
Afterward, toggle Airplane Mode or restart the phone so it creates a fresh connection.
3. Check the APN
The Access Point Name tells your phone how to enter the carrier’s data network.
Most eSIMs install it automatically.
Sometimes they do not.
Use the APN supplied with your exact package. Do not copy one from a forum because another traveller used the same brand; different destinations and plans may require different values.
On iPhone, the setting may appear under:
Settings > Cellular > Travel eSIM > Cellular Data Network
On many Android phones:
Settings > Network & Internet > SIMs > Access Point Names
Copy the spelling, capitalisation, username, and password exactly. Restart the phone if instructed.
Some iPhones hide APN editing. In that case, contact the eSIM provider rather than installing random configuration profiles.
When I entered the correct APN, the first webpage opened immediately.
No VPN was involved.
For the first time, I knew the road beneath the tunnel was actually open.
4. Try a Supported Network
Automatic carrier selection usually works, but some travel eSIMs support only specific local partners.
Your phone may register with the strongest carrier even though that carrier cannot provide data for your package.
Check the provider’s instructions. If partner networks are listed, select one manually and give the phone time to connect before trying another.
Once direct data works, stop changing eSIM settings.
The foundation is fixed.
If the eSIM Breaks Only When the VPN Connects
Reconnect the VPN using one nearby or recommended route.
For the first test, disable optional ad blocking, tracker filtering, and other extras. You are trying to isolate the tunnel, not test every feature at once.
Open:
- one ordinary website;
- one map search;
- one message;
- one small file or image.
Do not begin with streaming or repeated speed tests. They add noise before you know what is failing.
If everything stops again, disconnect the VPN and confirm that direct data still works. Mobile service can fail temporarily, and without that second check it is easy to blame the wrong layer.
When the VPN Says “Connected” but Apps Still Hang
A green VPN icon means the tunnel handshake succeeded.
It does not guarantee that every app has a usable route beyond it.
You may see:
- messages arriving while websites refuse to load;
- a map or banking app hanging;
- mobile data failing while Wi-Fi works;
- one app working and another timing out.
This often points to DNS, IPv6, or another privacy feature conflicting with the mobile network.
Do not immediately force the APN to IPv4-only or IPv6-only. A change that fixes one carrier can break another.
Instead:
- Try one other VPN route or connection mode.
- Return DNS to its automatic setting.
- Temporarily simplify other privacy layers.
- Test the same apps again.
On Android, set Private DNS to Automatic or briefly turn it off.
On iPhone, temporarily pause Private Relay or Limit IP Address Tracking for the travel line when applicable.
If the connection returns, re-enable those features one at a time.
The goal is to find the conflict—not to leave every privacy setting disabled because one broad reset happened to work.
DNS Can Fail in Two Opposite Ways
Sometimes the eSIM works only when the VPN is connected. In that case, the VPN may be routing around the carrier’s broken DNS.
Other times, direct data works and the VPN breaks it. Then the VPN’s DNS may be conflicting with Private DNS, Private Relay, another filter, or the carrier’s IPv6 setup.
Either way, the lesson is the same:
A working radio connection, a green VPN icon, and a working DNS path are three separate things.
Leave Network Reset Until Last
A full network reset may fix a stuck profile.
It may also erase saved Wi-Fi networks and reset the APN, cellular settings, and VPN configuration you have just repaired.
Before using it, save:
- the provider’s APN instructions;
- screenshots of cellular settings;
- VPN activation details;
- important Wi-Fi passwords;
- support contact information.
Try Airplane Mode, a restart, the correct data line, roaming, APN, partner network, and automatic DNS first.
Do not erase ten working settings because one of them is wrong.
Only Then Should You Compare VPNs
Once the eSIM works without a VPN, the product no longer has to rescue the mobile network.
It only needs to do something more realistic:
Disconnect cleanly, reconnect without disturbing everything else, and make it obvious whether the failure belongs to the eSIM or the tunnel.
A large VPN can be useful after the fault has a name. Multiple protocols, custom DNS, kill switches, and detailed controls give experienced users more ways to test compatibility.
Before the eSIM is working, however, every extra switch creates another suspect.
A reputable free VPN can also provide one useful comparison: does a second VPN work over the now-functional eSIM?
If it does, the original VPN or its DNS becomes the stronger suspect. If both fail in the same way, return to the carrier route, DNS, or IPv6.
Keep the test small. One server. One page. One message.
The goal is diagnosis, not rebuilding your entire setup beside a station gate.
The App I Had Forgotten About
I had installed it before departure during the same rushed session in which I downloaded offline maps and saved screenshots of the hotel address. By the time I reached the station, I had almost forgotten it was there.
It happened to be connected when the ticket failed, so I turned it off first.
Nothing changed.
That was useful. Once the VPN was gone and direct data still failed, I stopped blaming servers.
After selecting the correct line, enabling roaming, and repairing the APN, I tested the ticket, map, and messages without a VPN.
They worked.
Only then did I reconnect the app, with its optional filtering still disabled. The same three tests worked through the suggested route. One other app continued spinning until I returned DNS to automatic.
Then I stopped changing things.
The VPN had not repaired the eSIM. It had not selected the carrier partner or fixed the APN by magic.
It simply came back after the mobile connection was healthy without making the original problem harder to understand.
That mattered more than another page of server statistics.
The service has fewer advanced controls and routes than some large providers, so travellers who need manual protocols, exact-city selection, or detailed logs may prefer a broader tool. It also cannot promise compatibility with every carrier.
For me, the result was enough:
Direct data worked. The VPN worked afterward. I still knew what had fixed the problem.
A few days later, I noticed a small counter showing blocked tracking requests. I had kept the filtering feature off during troubleshooting, so it deserved no credit for the repair.
Once the emergency was over, though, quieter pages were a pleasant extra.
Not another switch thrown in the middle of it.
Test the Combination Before You Travel
Install and test the eSIM and VPN while you still have reliable Wi-Fi, email access, and time to undo mistakes.
Before departure:
- Save the APN and partner-network instructions offline.
- Learn how to select the travel line.
- Practise disconnecting the VPN completely.
- Reconnect it with optional filtering disabled.
- Test a website, map, and message.
- Make sure activation does not depend on a code sent to an unavailable number.
You cannot recreate every foreign carrier from home.
You can still eliminate missing instructions, forgotten credentials, hidden kill switches, and apps you do not know how to turn off.
Do not let the station gate become your first setup screen.
The Order to Follow
When an eSIM and VPN stop working together:
- Disconnect the VPN.
- Select the travel eSIM for mobile data.
- Enable roaming if the package requires it.
- Enter the provider’s exact APN.
- Try a listed partner network.
- Prove that direct data works.
- Return DNS and privacy settings to a simple baseline.
- Reconnect one VPN route with extras disabled.
- Try one alternative route if the failure repeats.
- Reset network settings only as a last resort.
If direct data fails, contact the eSIM provider.
If direct data works but the VPN fails, contact the VPN provider.
If the problem appears only on mobile data and disappears on Wi-Fi, mention the country, carrier, phone model, operating system, and possible IPv6 issue.
Five signal bars and a green VPN icon can both be telling the truth while answering the wrong question.
The most useful travel VPN is not the one that claims it can repair every network. It is the one you can remove from the equation, restore after the eSIM is healthy, and still understand when something breaks.
Questions I would have wanted answered
What should I test first when an eSIM and VPN stop working?
Disconnect the VPN, turn off Wi-Fi and prove that the travel eSIM can load a normal page on direct mobile data. This separates a carrier or eSIM problem from a VPN problem.
Can full signal and 5G still mean no usable internet?
Yes. Signal bars show that the phone can see a network, not that the active line, roaming, APN, partner route and DNS path are all correct.
Should I reset network settings immediately?
No. A full reset can erase saved Wi-Fi networks, APN values and VPN settings. Try the correct data line, roaming, APN, partner network, automatic DNS and a restart first.
What role does OnlyDogs VPN play in this troubleshooting order?
The article treats OnlyDogs VPN as something to reconnect after direct mobile data is healthy. It is not presented as a way to fix an incorrect APN, disabled roaming or a failed carrier route.
A few links I had open at the time
Apple’s APN support note and Google’s Private DNS help page.