A corrupted firmware download can cause the restore to hang and time out.
Always use an Apple-certified MFi cable. Third-party cables often fail during the heavy data load of a restore. 3utools error unable to restore idevice75 link
How to Fix 3uTools Error: "Unable to Restore iDevice (-75)" If you are trying to flash or restore your iPhone or iPad and hit the dreaded in 3uTools, you aren't alone. This error usually pops up during the "Sending Filesystem" or "Restoring" stage. A corrupted firmware download can cause the restore