iOS 16.3 not good for models earlier than 1P!2?????????????
Anybody had this problem???????
There is a model that is called: iPhone 12. It is not 1P!2. And there are iPhone models that are still running iOS 12, so without detailed information it is just about impossible to help (complete sentences will help too - these are technical forums and we are not good at guessing.
Just on a hunch, here are the requirements for iOS 16.3:
iOS 16 and iPadOS 16 are compatible with these devices - Apple Support