Users can no longer downgrade to iOS 16.3, a result of Apple no longer signing the iOS 16.3 update.
Apple released iOS 16.3.1 in mid-February and has stopped signing its immediate predecessor. As a result, any users who may be experiencing issues in 16.3.1, no longer have the option to downgrade, according to MacRumors.
The move is not at all uncommon, as Apple routinely stops signing older versions of its operating systems. This ensures users stay on the latest editions, which in most cases is a good thing.