When you use 3utools to update your iOS device, it requests the SHSH blob from Apple's servers to validate the firmware. However, if the request fails, you encounter the "Unable to request SHSH" error.
To tailor these steps further, let me know your , the iOS version you are trying to install, and whether you are aiming to upgrade or downgrade . how to fix error unable to request shsh on 3utools when upd