PASSCODE EXPIRED

It isn't if your phone is associated with a school or corporation email or has a configuration profile at Settings > General > VPN & Device Management (and you are aware of the relationship to that profile).

Also see: Install or remove configuration profiles on iPhone - Apple Support

Normally an iPhone passcode doesn't expire but if your phone has a configuration profile (associated with a school or corporation, sometimes required when using a school or corporate email address) they may enforce a requirement to periodically change the passcode. Also see: Install a configuration profile on your iPhone or iPad - Apple Support