Link Upd — 3utools Error Unable To Restore Idevice75
3uTools Error "Unable to Restore iDevice (Error 75)": Causes and Fixes
Then reboot and reconnect iPhone.
Are you trying to update the device while keeping data, or are you performing a full "Quick Flash" to wipe it?
ERROR: Unable to restore iDevice(-75). - Apple Community 3utools error unable to restore idevice75 link