HTC 1 saying no SIM Card

You have either a bad SIM card, a bad SIM card socket, a bad connection between the SIM card socket and the board it's soldered to, a bad board, or your account is improperly provisioned (or, VERY rarely, your carrier lost all data in that area). That's about as far as we can go with the information you provided, so unless you can troubleshoot the problem further, your best bet (unless you can borrow someone else's SIM card on the same carrier to try in your phone, or someone else's phone on the same carrier to try your SIM card in [and they'd have to use the same size card]) would be to bring the phone into one of your carrier's stores and see if they can tell you what's wrong.

 

Hi, you haven't said whether you've done a restart or not. I had exactly the same problem about a week ago. After 5 months of use and completely out of the blue my One did the same. I didn't disturb the SIM card but went straight for a reboot and it came up no problem.

It's worth trying if you haven't done already.

Good luck.