In short, this error occurs when 3uTools cannot communicate with Apple’s servers (or TSS servers) to verify the firmware you are trying to install. Here is a comprehensive guide on why this happens and how to fix it. What is an SHSH Blob?
Look at the list of available firmwares. If the version you want does not have a green "Signed" status (or if it's explicitly marked as unsigned), you cannot flash it unless you have previously saved SHSH blobs for that specific device. 2. Update 3uTools and iTunes Compatibility issues can trigger server errors. 3utools Error Unable To Request Shsh
Apple has stopped supporting this version. In short, this error occurs when 3uTools cannot