https://wccftech.com/ios-14-7-ipados-14-7-no-longer-being-signed-downgrade-not-possible/

Apple is no longer signing iOS 14.7 and iPadOS 14.7 for iPhone and iPad users. You can no longer downgrade from 14.7.1 update.

It was only yesterday we asked our readers to downgrade to iOS 14.7 or iPadOS 14.7 as Apple was still signing the older firmware. Today, all of that changes as the company has stopped signing said firmware. This means you have to stick with whatever you already have on your device or the latest iOS 14.7.1 and iPadOS 14.7.1 updates.