To fix this error, it helps to understand what SHSH blobs are and why 3uTools might fail to retrieve them. SHSH (Signature HaSH) blobs are digital signatures that Apple uses to verify that any iOS firmware being installed on a device is official and authorized. Think of them as a unique, time-sensitive permission slip from Apple. You can only request this permission slip while Apple is actively "signing" that specific iOS version.
If the request fails while the phone is in "Normal" or "Recovery" mode, try putting the device into . This is a deeper state that often bypasses software communication errors. 3utools error unable to request shsh hot