Why is phone not seeing my SIM card intermittently
iPhone 5s
It could be for any reason, since you do not state that you have done any troubleshooting. See this support document for troubleshooting steps for no SIM. iPhone: Troubleshooting No SIM
I Tried steps 1,2,3 and it suddenly started working . Then I turned phone off and 1 hour later same dumb problem. This time steps 1-4 don't work so I will need to find tiny key to get it out. It seems I will need a new card.
See your carrier, they can replace the card. Also, you can use the end of a straightened paper clip in the SIM tray hole. That will release the tray.
Why did my 5s stop finding my SIM card
