On recent iOS versions, SHSH blobs are no longer used in the same way for regular restores. 3uTools may show this error even when trying to restore a signed version due to Apple’s enhanced security (T2 chip, Secure Enclave, etc.). In such cases, instead – they handle SHSH requests natively without exposing the error.
3uTools frequently updates its "Flash" and "Pro Flash" modules to keep up with changes in Apple's server protocols. If you are running an older version of 3uTools, it may be sending outdated requests to Apple. how to fix error unable to request shsh on 3utools when upd