When Apple issues a signature, it is tied to a random number called the ApNonce (Application Nonce). 3uTools sometimes requests a blob with a generic ApNonce, but later when you try to use that blob for a restore, your device generates a different ApNonce. The signature doesn't match. As a defensive measure, Apple's servers may reject 3uTools' request outright if the ApNonce format is incorrect.
If you are trying to downgrade to an version and keep getting this error, 3uTools cannot "fix" this automatically. You can only proceed if: i unable to request shsh 3utools fix better
(found in the "Info" section of 3uTools), and request an AP ticket for your target firmware. If the site shows the version is unsigned, then no software tool will be able to flash it. 5. Check Your Connection & Host Files When Apple issues a signature, it is tied
How to Fix "Unable to Request SHSH" Error in 3uTools If you encounter the error (often at the 9% mark) while flashing or restoring your iPhone, it typically means 3uTools cannot communicate with Apple’s servers or verify the firmware version you are trying to install. 1. Update 3uTools to the Latest Version As a defensive measure, Apple's servers may reject
Visit sites like sh.host to see if blobs for your device were ever saved to public servers.
If the above steps don't resolve the issue, you can try using a different tool to request SHSH blobs. is a popular alternative tool that can help you request SHSH blobs.