Apple recently released iOS 14.7.1, and as is traditional, Apple has now stopped signing iOS 14.7, making downgrading to that version of iOS no longer possible.
Apple last week released iOS 14.7.1, which provided the following fixes:
iOS 14.7.1 fixes an issue where iPhone models with Touch ID cannot unlock a paired Apple Watch using the Unlock with iPhone feature. This update also provides important security updates and is recommended for all users.
An Apple support document said iOS 14.7.1 addresses a serious security vulnerability that may have been exploited in the wild.
Apple is known to routinely stop signing older versions of operating systems after it releases a public update, as part of an effort to encourage users to keep their devices’ operating systems up to date. Restoring devices to older iOS builds is common for users with jailbroken devices.