3uTools is a popular third-party tool for managing iOS devices, including flashing (updating/downgrading) firmware. During the flashing process, 3uTools attempts to request from Apple's servers. SHSH (Signature HaSH) blobs are digital signatures that Apple issues to verify that a specific firmware version is authorized to run on a specific device.
Corrupt or missing Apple drivers can prevent SHSH negotiation.
The "Unable to request SHSH" error typically occurs during these actions:
If you absolutely need to keep data, "Easy Flash" is sometimes more forgiving than "iTunes Flash."