If 3uTools is requesting SHSH successfully but the installation fails halfway through, or if the "Unable to request SHSH" error persists, you may need to force a proper connection.
Check which versions are still signed on sites like ipsw.me . i unable to request shsh 3utools fix install
If 3uTools continues to fail, try performing a standard restore using the official iTunes or Finder application. If 3uTools is requesting SHSH successfully but the