Short answer
If the phone does not connect to a network, it may be outside the covered area, connected to the wrong local network, or missing required settings.
Check first
You are in a supported country/region for your plan.
The eSIM line is turned ON.
The eSIM is selected for Mobile Data.
Data Roaming is ON for the eSIM.
If automatic network selection does not work
You may need to try manual network selection, depending on available local networks.
If still not working
Contact support with screenshots of your eSIM settings, Network Selection screen if available, and your current country/city.