Follow the on-screen 3uTools guide to enter (the key combination varies by iPhone model).
For advanced users, you can manually verify if your device's EID or ECID matches the firmware requirements by visiting sh.host.io 3utools Error Unable To Request Shsh
The error occurs when 3uTools fails to retrieve from Apple’s TSS (Telephony Signing Server) or local cache. Primary technical causes: Follow the on-screen 3uTools guide to enter (the
Firewalls, antivirus software, or an edited "hosts" file can block the connection to Apple. the request is automatically denied
If you are trying to install a version Apple is no longer signing, the request is automatically denied, and 3uTools will show the error.