You can recover the lost data from the backup. Sometimes you may encounter data loss after upgrading the iOS version.
If your iPhone storage is full, see our post on how to free up space on iPhone.
Software update requires enough space on your iPhone. When it finishes downloading, tap Install.
If it asks for your device passcode, do it.
You can check for and install a carrier settings update as follows. Carrier settings updates will improve the cellular network connectivity and performance of your iPhone. This method is not very common, but you can have a try.
Software Bugs: Some unknown bugs or glitches can inflict several forms of iPhone malfunctions.SIM Card Issue: If the SIM card is out of position, blotted, or frayed, then your iPhone cannot recognize it.Let’s see the specific reasons behind the alert that says Invalid SIM or No SIM Card installed on iPhone. When you have such a problem, there are mainly three causes you should consider. Common Causes of iPhone Keeps Saying No SIM Card 6 Ways to Fix iPhone Says No SIM Card Issue Common Causes of iPhone Saying No SIM Card