Following the release of iOS 13.6.1 last week, Apple today has stopped signing iOS 13.6. That means users can no longer downgrade from iOS 13.6.1 to iOS 13.6.
Reverting to older iOS builds is common for those with jailbroken devices and can sometimes also be helpful for users who experience significant bugs after upgrading to the latest version of iOS.
According to Apple, iOS 13.6.1 fixes some known issues related to the Exposure Notifications and another one that could make the displays exhibit a green tint. The update was released last Wednesday for all users.
Prior to that, iOS 13.6 was released in July with Car Key, a digital key that will work for locking, unlocking, and starting supported vehicles. The update also introduced Apple News+ Audio with professionally narrated audio stories curated from the Apple News team to your device.
Now that Apple has stopped signing iOS 13.6, users can no longer downgrade to that version of iOS from a newer version. By preventing users from reinstalling older versions of iOS, Apple ensures that customers are getting the most stable experience currently available.