Why Does My Phone Say Invalid Sim |work| Link

If your software is outdated, it may be incompatible with recent carrier settings updates.

If you just bought a phone and put your old SIM in: why does my phone say invalid sim

This forces your phone to reset its connection to the cellular network. If your software is outdated, it may be

The root cause is usually one of three things: the physical card, your phone's software, or your service provider. If your software is outdated

: Settings > System > Reset options > Reset network settings.