iPhone 7 Cannot Activate

I have an iPhone 7 and since yesterday I haven't been able to connect to the carrier/mobile network. I cannot receive any calls or use cellular data. However, I was able to use the phone with WiFi and communicate via Whatsapp.

I have tried many of the recommended techniques to solve the issue but finally decided to restore the iPhone. It had the latest iOS 13.3 on it. Now, unfortunately I am unable to activate the iPhone because it cannot detect the SIM card/mobile network (see photo). I cannot get into the phone at all and obviously can't even use my apps with WiFi.

Is there a way I can get into the phone without SIM/mobile activation?

An urgent help will be appreciated.

I am in lockdown - cannot get another phone and I am not able to contact friends/family outside.

Thank you a lot.