In my iPhone not Coming Sim network showing not valid Sim please do some thing
In my iPhone 8 not coming Sim card showing Sim not valid please do something Sir
The phone is locked to a cellular carrier other than the one you are trying to use.
If you don't know what carrier it's locked to, ask whoever you got it from or call AppleCare and give them the serial number.
Only the carrier it is locked to can unlock it for use on other carriers.