Alex remembered that Apple only "signs" certain firmware versions. If Alex was trying to downgrade to an iOS version that Apple had already "closed," the SHSH request would always fail because the server refused to provide the necessary digital key. Alex checked a site like
This error typically appears when you tick the version option (or try to fetch SHSH blobs) in the "Flash & JB" section. When this happens, the process stops immediately, and your device may be stuck in recovery mode. how to fix error unable to request shsh on 3utools when top