sim card not installed

I'm having the same problem. New iPhone. From day 1 I'm experiencing "Sim Card Not Installed" issues which comes and goes randomly. In some cases my phone was at rest on the table and my screen turned on to show "Sim Card Not Installed" then moment later the SIM card worked and that repeated few times. I've removed my SIM card and cleaned the contact surface to ensure there is no oxidation on the SIM card. I've popped it back in, it worked for some time and soon after I got the same message. I have a simple dumb phone, which never had problem using this SIM card.

I read suggestions to switch on and off the airplane mode / restart phone / re-insert the SIM card.. but those are not proper solutions.

I was always on the latest iOS version. Until today I was on 15.1. Today after receiving push notification about update for 15.1.1 I updated right away. Hour after that I got another similar occurrence. Right now the SIM is found after i switched off/on the airplane mode.

Take your SIM card out and gently clean it. Contact your carrier for help with this as needed.