3uTools is great, but it’s not the only tool. Use the online TSS Saver ( tsssaver.1conan.com ) to fetch blobs using your device ECID. This bypasses 3uTools entirely.

Look for the firmware version you want to install. If it does not have a green "Signed" status next to it, the "Unable to Request SHSH" error is expected because Apple is no longer authorizing that version.

Verify your firewall or antivirus isn't blocking 3uTools' access to the web.

The most frequent reason for this error is trying to flash a firmware that Apple is no longer signing. Open 3uTools and go to the tab.