If your phone shows “No Service” after landing, begin with the simple checks. Confirm that flight mode is off, the travel line is switched on and mobile data is assigned to that line. A brief restart can also help the phone register with a local network after leaving the aircraft.
If the connection is still missing, open the mobile-network settings and check whether automatic network selection is enabled. Some destinations work better after choosing one of the available partner networks manually. Make sure data roaming is enabled for the travel eSIM when the plan instructions require it; this setting is separate from the roaming setting on your primary line.
Avoid deleting the eSIM while troubleshooting unless support specifically asks you to. Many eSIMs can only be installed once, so removing a profile may make the problem harder to fix. Check the plan coverage and allowance, connect to Wi-Fi if possible and contact support with the phone model, destination and exact error message.