A short tutorial on how to fix the “No SIM” or “Invalid SIM Card” error you get when you put your SIM card into your iPhone or iPad. Read out this tutorial and do what it says to fix the problem with your SIM card. Follow the instructions below.
It should switch over automatically, but if your device is using an eSIM, for example, it might not use the SIM card you put in.
Under Data Plans, make sure that your primary plan is enabled and that all other settings are set to their default values. Ensure that you have an active plan running with your wireless carrier.
Update & Restart iPhone
If this is the case, and the issue is not related to the card itself, then head to your General settings. Here, tap on Software Update and make sure that your iPhone is running the latest iOS update.
After downloading and installing the update, make sure to restart your device. Restarting your iPhone will restart all processes, which can in a lot of cases fix the SIM card error you are getting.
Remove & Replace SIM Card
If nothing else works, take out your SIM card to see if it fits right. You could try a different SIM card, like one from a family member, to see if that helps fix the error. In this case, the problem is with your SIM card, so you should get a new card with the same number or, even better, try getting an eSIM.
Reset Network Settings
Lastly, if you ever changed some mobile data settings or if you recently changed your location, then it might be a good idea to reset your network settings. In your General settings, scroll down and tap on Transfer or Reset iPhone.
Select Reset and then Reset Network Settings. After entering your passcode, your iPhone will restart with the factory network settings, which will in a lot of cases fix the SIM card error you are getting if the problem is not related to the card itself.