USIM APN and Data Settings After Activation

TL;DR

• APN = access point name for data. Wrong or missing APN → data may not work even with signal.
• After activating eSIM (or local USIM), if data doesn’t connect, check provider email/app for APN and enter it in device settings (Cellular > eSIM > Cellular Network on iPhone; SIM > Access Point Names on Android). Reboot after saving.
• Provider-specific—use the value from your plan’s provider. See eSIM APN manual setting, Data not working abroad.