my Iphone 12 pro suddenly shows No sim, same sim is working in another phone, i verified with two different phones, what could be the problem

Hey imthyas1979,

Thanks for using Apple Support Communities. We'd be happy to help out. If you're noticing a No SIM error on your iPhone 12 Pro, the following steps are best equipped to assist with that:

If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad

If you get an alert that says Invalid SIM or No SIM Card installed, follow these steps.

1. Make sure that you have an active plan with your wireless carrier. 

2. Restart your iPhone or iPad.

3. Check for a carrier settings update. Go to Settings > General > About. If an update is available, you'll see a prompt to select OK or Update.

4. Remove your iPhone SIM card or iPad SIM card from the SIM card tray and then put the SIM card back. Make sure that the SIM tray closes completely and isn’t loose. If you use a SIM tray from a different model iPhone, iPad, or from another phone manufacturer, it might not fit properly.

5. Try using another SIM card. If you don't have one, go to your carrier's retail store and ask them to test with another SIM card. You might need to replace your SIM card.

If you still see an alert about your SIM card, contact Apple support.

This is all outlined further here: If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

We hope this helps out.

Take care!