If your iPhone says "No SIM" or "Invalid SIM," it could be an issue with your SIM card or the device not recognizing it. Here are some steps to troubleshoot:
Restart Your iPhone or iPad.
Check for Software Updates:
Go to Settings.
Tap General.
Tap About. If there's a software update available, select OK or Update to install it, as this might resolve the issue.
Remove and Reinsert Your SIM Card:
Carefully take the SIM card out of the tray and gently replace it.
If you’re still seeing the "No SIM" or "Invalid SIM" message after trying these steps, please contact Apple Support for further assistance.