The iOS 14 version that Apple introduced to users on September 16 was highly appreciated in general. Currently, the release of the iOS 14.2 Public Beta and the skipping of the 14.1 Beta are considered an indication that things are on track. With just 1 week since the release of the new iOS version, signatures for iOS 13.7 version have been closed.
Signatures closed for iOS 13.7 version!
Signing has been disabled for iOS 13.7. This also means that all iOS 13 versions are unsigned. So, you are not allowed to upload an iOS 13 IPSW file to your device via iTunes.
If you upgraded your phone to iOS 14 either on the device or via iTunes, you will now need to continue with this version.
It is also worth remembering that backups taken with iOS 13 via iTunes cannot be restored to devices from now on. You can only restore your data from your iCloud backup — other than device backup.