This is what I did to fix the No SIM Card Installed Error on my Samsung Galaxy S6. I hope this helps you… [Step 1] Remove the back cover of the phone. [Step 2] Remove the battery. [Step 3] Remove the SIM card.
If your phone is a Samsung Galaxy, you can try to restart your phone by holding down the power button for a few seconds, and then selecting “Turn Off Power.” If you are able to restart your device, try reinserting the SIM card.