Short answer: when a travel eSIM shows No Service, or has bars but no internet, in Korea, check your phone’s settings before you assume the eSIM is broken. Holafly’s general troubleshooting guide puts it this way: “If your eSIM is not working, the fix is usually one of four things: data roaming is switched off, the eSIM isn’t set as your active data line, the APN settings are wrong, or your phone is locked to a carrier.” Airalo, Holafly and Klook each give the same kind of checklist in their help pages. Below, we put their steps in one order. One rule comes first: do not delete the eSIM while you troubleshoot.
Last checked: October 13, 2026. We read the troubleshooting pages of Airalo, Holafly and Klook, Airalo’s and Holafly’s South Korea pages, and Apple’s support pages. We did not buy, install or test any eSIM for this guide. If you have not bought an eSIM yet, start with our guide to choosing a Korea eSIM.
Quick answers
| What you see | Possible causes | What to try |
|---|---|---|
| No Service or Searching | You have just landed, the eSIM line is off, or the phone has not picked a network | Wait a minute after landing, then work through Steps 2 to 5 below |
| Bars, but no internet | Data roaming is off for the eSIM, or your home SIM is still the data line | Make the eSIM the data line and set Data Roaming as your seller says. On Android, turn your home SIM off first |
| Still no internet after that | The APN may need to be entered by hand | If your seller’s instructions list an APN, enter it exactly |
| An error while installing | The phone is carrier-locked, already holds too many eSIMs, or the eSIM was installed elsewhere | On an iPhone, check Carrier Lock under Settings > General > About |
| It worked, then stopped or slowed | Your data or days may have run out, or the signal is weak | Check the remaining data in your phone’s settings |
Before you start: do not delete the eSIM
This is the step that can turn a settings problem into a new purchase.
- Holafly: “Your eSIM card for South Korea can’t be transferred or reinstalled once it’s installed.”
- Klook: “Please be careful not to remove the eSIM once you’ve activated it.” If you remove it after you started using it, Klook says “you won’t be able to restore it and will need to purchase a new eSIM.”
- Airalo says deleting the eSIM removes it from your device, and you cannot use packages on that line until you add the eSIM again.
The same goes for the iPhone’s “Delete All eSIMs” reset. Apple says that after it, “You will need to set up a new eSIM or physical SIM card to connect to a cellular network.” Our suggestion: if you want the eSIM out of the way, turn the line off instead of removing it.
Step 1: Are you in Korea, and has it had a minute?
Airalo and Holafly both tie activation to being there. Airalo’s troubleshooting page says: “Verify that you have arrived in your destination country—packages only activate within covered regions.” Holafly’s Korea page says: “The Holafly data plan will only be operational once you arrive at your destination.”
Right after landing, give the phone time. Holafly says: “If you’ve just landed, give it a minute to find a local network before trying anything else.”
Step 2: Is the eSIM line turned on and set as the data line?
An installed eSIM can sit there switched off. On an iPhone, open Settings > Cellular, tap the eSIM line, and check that the line is on. Apple says: “If the cellular line is off, tap Turn On This Line.”
Then make the eSIM your data line. Airalo’s iPhone steps say: “Go back to Cellular/Mobile Data and select your eSIM as the data line.” Klook’s checklist for Android says: “Double-check if you selected the eSIM as your mobile network.”
Airalo also tells iPhone users to switch one more setting off: “Turn Allow Cellular Data Switching off.”
Step 3: Is Data Roaming set right for the eSIM line?
This is the setting all three sellers name. First, keep your home line from roaming. Airalo explains the difference between phones: “For iOS devices, you can turn on data roaming for individual SIMs — make sure it’s turned off for your primary SIM to avoid roaming charges.” On Android, Airalo says “data roaming usually applies to all SIMs in use — make sure you have your primary SIM turned off to avoid roaming charges.”
So on an iPhone with two lines, change roaming on the eSIM line only. Apple’s path is: turn on Cellular Data, “tap the number you want to modify, then tap Cellular Data Options.” On Android, turn your home SIM off before you turn roaming on.
Then set roaming for the eSIM as your seller says:
- Holafly’s Korea page: “To ensure that your eSIM gets the best coverage, you must turn on data roaming on your phone’s settings.” Its general guide adds: “Then go to your eSIM profile and make sure data roaming is turned on there as well.”
- Klook: “Make sure the data roaming is turned on: toggle on “Data Roaming” from the eSIM settings.”
- Airalo: its newer troubleshooting page says, “In your device settings, make sure Data Roaming is turned on for your eSIM line.” Its older iPhone page says to “Toggle Data Roaming ON or OFF as instructed in your Airalo app,” so check what your plan’s instructions say.
Step 4: Restart the connection
Turn Airplane Mode on, wait, and turn it off. Apple says: “If your cellular network is available, you might be able to reconnect by turning Airplane Mode on and off.” Airalo’s “New Airalo” troubleshooting page says to keep Airplane Mode on for 10 seconds, and its page on slow internet says to wait 30 seconds. Our suggestion: wait 30 seconds. If that does not help, restart the phone.
Step 5: Pick the network by hand
If the phone does not settle on a network, turn off automatic selection and choose one yourself. Klook says: “Try turning off the automatic network selection and select the supported carrier manually.” The paths, from Holafly’s guide:
- iPhone: Settings > Cellular/Mobile Data > Network Selection > turn off Automatic > select a network.
- Android: Settings > Connections/Network & Internet > Mobile Networks > Network Operators > turn off Automatic > select a network.
Which network to pick depends on your plan, so use the one your seller names. Airalo says to “Select the network shown in your Airalo app connection instructions.” On October 13, 2026, Airalo’s South Korea page said: “Operates on the SK network in South Korea.” If your phone shows a different Korean network, switch to the one your plan names.
On Samsung Galaxy phones, Airalo lists choosing the network as step 2, before the APN.
Step 6: Check the APN
Airalo explains: “APN stands for Access Point Name. It tells your device how to connect to the internet.” Holafly says: “In most cases, the APN details fill out automatically when setting up the eSIM.” Not always, though.
- Airalo: “Some Airalo eSIMs require you to manually update your APN settings in order to access data.” It adds: “If the APN is not listed, it means your eSIM is configured automatically, and no further action is required.” When there is one, “Enter the APN exactly as shown in your eSIM installation details (all lowercase, no spaces),” and “If it does not connect immediately, restart your device to apply the new settings.”
- Holafly: “You’ll receive the correct APN settings via email with your activation QR code.”
We are not listing APN values here. Use the APN given for your own eSIM, from the app or the email that came with your order.
Step 7: Update the phone’s software and carrier settings
- Carrier settings (iPhone). Apple says to make sure the phone is connected to Wi-Fi, then open Settings > General > About. Apple says: “If an update is available, you’ll see an option to update your carrier settings.”
- “3G” next to the signal bars. Klook says: “If “3G” is displayed beside the signal bar, try upgrading the iOS software to the latest version.”
Step 8: Reset network settings, as a last step
Resetting network settings clears your saved Wi-Fi networks and passwords and your APN settings, according to Airalo. Airalo says: “you should only reset your network if you’re comfortable reentering all of the listed settings.” On an iPhone, Apple’s path is: “Tap General, tap Transfer or Reset iPhone, then tap Reset,” then choose Reset Network Settings. Do not choose Delete All eSIMs.
After the reset, check Data Roaming again. Apple’s own page on the reset says: “Cellular data roaming may also be turned off.” If it is off and your plan needs it on, set it again as in Step 3. If your eSIM needed an APN in Step 6, enter it again too.
If it fails while installing
Klook’s help page lists three error messages and what they mean:
- “Cellular Plans from This Carrier Cannot be Added”: “Your device might be locked to a specific carrier.” On an iPhone, check Settings > General > About > Carrier Lock. Klook says it should read “No SIM restrictions.” Airalo says carrier locks “will prevent your eSIM from being set up or connecting,” and Klook says to “contact your original carrier” about it.
- “Unable to Complete Cellular Plan Change”: “Please double-check if your device has reached the maximum eSIM capacity and remove unnecessary eSIMs.” Remove old eSIMs you no longer need, not the new one.
- “This code is no longer valid”: “Please make sure that the eSIM has not been already installed on another device.”
If it worked, then stopped or slowed
- Out of data or days. Klook says: “You may have used up all your data.” Holafly’s Korea page says: “If you use all your data or run out of days, your eSIM card will no longer work and you will lose internet connection.” Klook also warns: “The data balance displayed in your booking details is not updated on a real-time basis.” It says: “Please double-check if you have remaining data from the device’s settings.”
- Weak signal or a busy network. Klook suggests you “Move to a less-crowded space or a location with a better signal.” Airalo lists “Carrier prioritization (local carriers may give priority to their own users)” as one reason a travel eSIM can be slower.
- Holafly’s coverage note for Korea says coverage may be “more limited or unstable on high-mountain trails.”
What the status in the app means (Airalo)
Airalo’s app shows two statuses that help you see where you are stuck:
- Installed: “The eSIM profile has been successfully downloaded and configured on your device.”
- In Use: “The eSIM has successfully connected to a mobile network and initiated a data session.”
Our suggestion: if it says Installed but not In Use, go back to Steps 1 to 6.
When to contact the seller
If you have done Steps 1 to 8 and it still does not connect, contact the seller before you delete anything.
- Airalo: “please contact us via chat in the app or on the website.”
- Holafly: its Korea page says, “Our eSIMs generally work fine, but if you experience connection issues, we can provide you with a full or partial refund.”
Have your phone model, what the status bar shows, and which steps you already tried. If an app’s text-message code does not arrive, check whether your plan includes texts at all. Airalo says: ““Data Only” plans do not include calls and texts.” Our guide to choosing a Korea eSIM covers which eSIMs come with calls and texts.
If you would rather change to a physical card, read our Korea SIM card guide first.
What we did not test
We did not buy, install or activate any eSIM for this guide, and we did not try these steps on a phone in Korea. The steps and quotes come from the help pages of Airalo, Holafly, Klook and Apple, read on October 13, 2026. Where we explain why a step matters or suggest an order, that is our reading. The iPhone and Android paths differ, and menu names can vary (Airalo writes “Select Cellular (or Mobile Data).”), so follow your seller’s instructions for your own plan when they differ from this guide.