The Invalid SIM error message means the phone is ‘locked’ to one network and that a SIM card from another network has been inserted.
To use a SIM card from another network operator, the mobile phone needs to be unlocked.
Similar error messages include:
No SIM
SIM not recognised
Non valid SIM
SIM error
If the phone is unlocked and one of the above error messages is displayed, it can indicate a fault with the SIM card or the SIM hasn’t been inserted correctly.
