FOR iOS
Check if Data Roaming is Enabled
Go to iOS Settings.
Select Mobile Service (or Cellular on some iPhone devices).
Tap on the installed eSIM.
Enable Data Roaming.
FOR ANDROID
Enable Data Roaming
Go to Settings.
Tap Network & Internet.
Select SIMs (or SIM cards / Mobile networks).
Toggle Roaming (or Data roaming) On. (On some devices, this is called "International roaming," and it may need to be set to 'always active'.)