If "Easy Flash" fails, try using the "iTunes Flash" option within 3uTools, as it uses different protocols that may bypass the bug.
to verify your device's EID and ensure the firmware version matches what is available on their database. Why This Error Happens Unsigned Firmware: How To Fix Error Unable To Request Shsh On 3utools When
In this article, we will explain this error happens and provide nine proven solutions to fix “Unable to request SHSH on 3uTools when trying to flash, jailbreak, or save blobs.” If "Easy Flash" fails, try using the "iTunes