What does it mean - Invalid SIM?
iPhone 8 Plus
If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support
If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support
Thanks - but I don’t understand - I have not tried to switch carriers or done anything different to my phone.
it now says No SIM but still works.
if I turn it off and then on again - works fine for awhile - then the No SIM or INVALID SIM pops up again?
It means your device is locked to a different carrier than the sim you are trying to use.
Your phone is carrier locked and you can't use a different carrier until you unlock it from the last one.
INVALID SIM appears top left of phone
