Prometheus, the program that allowed to downgrade or upgrade iOS on iPhone and iPad, was blocked by the Apple company just one day after the official launch. Although yesterday some users enjoyed the possibility to downgrade or upgrade to certain versions of iOS, today this has been blocked by the Apple company for everyone.
More precisely, those from Apple made some changes for the TSS servers that sign the ipsws for installation in the iPhone or iPad, so that Prometheus no longer works. Nobody knows for now what kind of changes Apple made and it doesn't really matter because everything was blocked, apparently without a very simple solution.
If you try to use Prometheus at the moment, you will be stuck with blocked terminals because unsigned ipsws cannot be installed. Basically, go back to the previous situation, when Apple forces us to restore only to iOS 10.2 and absolutely nothing else, Prometheus becoming completely useless, even though it wasn't very useful from the very beginning.
There are rumors that these problems are temporary and that Apple will soon sign all iOS firmwares for iPhone and iPad, but you should not rely on such a thing. Apple has most likely blocked Prometheus as a security measure for iOS, so it's hard to say if the program will ever be useful for anything.
UPDATED: The creator of Prometheus claims that his program still works without problems.
.@phumiphat_k yes it still works. I used it multiple times today to downgrade my i5s to 10.1.1 today.
- tihmstar (@tihmstar) December 30, 2016
