So the SIM is not activating? That is strange, have you confirmed settings in System Settings > Network and internet > SIMs > your sim? (mobile data on, APN correct, VoLTE enabled, etc)?
I’m curious, does Android offer other networks/carriers if you choose “select manually” instead of “auto”?
And are you able to connect to a different carrier? But watch out with mobile data as I don’t know your roaming conditions..