If your iPhone dropped download to the floor by accident unfortunately, iPhone may ask to re-register your iPhone SIM card. To fix it, you can turn off the Airplane mode in the control center.
If you have enable the Airplane mode, the features of networks and phone calls will be disabled, and you might get the no SIM card error on your iPhone screen.
How to Fix iPhone Not Detecting SIM Card with Ease How to Fix Error 6 while Restoring iPhone? Part 2. So, please use your device in a proper environment. Because temperature and moisture can influence the performance of device. If your iPhone gets overheated or wet, No SIM card issue may also happens. If yes, please contact your carrier to get a new SIM card instead. Please make sure your SIM card is not damaged or useless. You can take it out of the slot and then clean up the SIM card and the card slot as well, then put it back into the slot again. If you have inserted the SIM card into the card slot but iPhone still says "No SIM card", please make sure you have cleaned the SIM card before your put it into the card slot, or the dust may influence the SIM card detection on iDevice. No matter it is or not, please try to reboot your device, trying to get rid of this problem. Sometimes if there are something wrong with the iOS system, it may fail to detect the SIM card on your iPhone, iPad or iPod touch. There are several main causes which lead to the issue that iPhone can not detect the SIM card into it. How to Fix iPhone Not Detecting SIM Card with Ease Part 1. So please read on to solve your doubts and find your solutions. So you might be curious the reasons of this problem and wondering how to fix it. Without fixing this problem, you can not make a phone call, send a text message, connect to cellular data and etc. But in fact, there is a SIM card in their iOS device. Sometimes Apple users may receive the alert, saying like "No SIM Card Installed", "Invalid SIM Card" or Insert SIM Card" from their iPhone/iPad/iPod.