"No service"-message on my iPhone after switching phones

Hi, I’m having an issue with my KPN SIM card on my iPhone.

My KPN physical SIM suddenly shows “No Service” and I can’t connect to the KPN network. I have already restarted the iPhone and tried turning Airplane Mode on and off. After turning Airplane Mode off, the phone starts searching for a network, but it never connects.

I also have eSIM from different provider in the same iPhone, and it works perfectly, so the phone itself seems to have a working mobile connection.

Does anyone know what could be causing this?