: Firmware versions with a green "Signed" tag or a distinct checkmark can be flashed freely. Versions marked in red or labeled "Unsigned" cannot be requested normally.
An unstable internet connection or firewall settings preventing communication with Apple's verification servers. Server Maintenance: 3utools Error Unable To Request Shsh
attempts to request these SHSH blobs from Apple’s servers (or from local backups/Cydia servers) before flashing. If it fails to get a valid signature, it throws the error: "Unable to Request SHSH." : Firmware versions with a green "Signed" tag