After the launch of iOS 16.2 on December 13, Apple has stopped signing iOS 16.1.2, the previously available version of iOS. With iOS 16.1.2 no longer being signed, it is no longer possible to downgrade to an earlier version of iOS after installing the iOS 16.2 update.
Apple routinely stops signing older versions of software updates after new releases come out in order to encourage customers to keep their operating systems up to date, which means it is not unusual that the updates are no longer being signed.
