I cannot add esim to iPhone 12

Hi, I am unable to add an eSIM to my iPhone 12 with iOS 16.6. I cannot enter Settings -> Mobile Data as it is greyed out (with message "No Sim"), and scanning a QR code from my provider with the camera app does nothing (it recognizes the QR code, but nothing happens when tapping the small yellow box).

I have tried putting in a physical sim-card which works, but still I am not able to add with camera app and QR code. I am in this case able to go into Settings -> Mobile Data, but here there is no Add eSIM option, as I have with my other iPhone (12 mini).

The model number starts with MG and I can see two IMEI numbers (IMEI and IMEI2) in Settings -> General -> About.

I have tried a full restore, without it changing anything.