SIM card saying not valid.
When I turn on my phone, such a screen comes up because the sim is not valid, but I plugged in another line and it says the same.
[Re-Titled by Moderator]
iPhone SE, iOS 15
Remove your SIM card from the SIM card tray and then put the SIM card back. ... Make sure that the SIM tray closes completely and isn't loose. If you use a SIM tray from a different model iPhone, iPad, or from another phone manufacturer, it might not fit properly.
If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad ...
