Re-download the firmware (IPSW) file. A corrupted file will cause a restore to fail.
An outdated program architecture cannot communicate with newer iOS kernels.
While not the same as Error 75, a related error many users see when trying to flash while preserving data is . This specific error ("Attempting to flash the device while preserving data will result in...Unable to restore device (-1110)") occurs when the device's internal storage is completely full, preventing iOS from performing a necessary filesystem check. 3utools error unable to restore idevice75 link
3uTools Error "Unable to Restore iDevice(-75)": Causes & Fixes
A corrupted or incorrect firmware file is a common cause of a failed restore. Re-download the firmware (IPSW) file
: In some cases, if the restore consistently fails at 20%, it may indicate a hardware fault with the NAND chip itself. 4. Use DFU Mode with a Clean IPSW
Are you trying to a disabled device?
or high-quality alternatives like a PlayStation charging cable. Plug the cable directly into the computer's motherboard USB ports (on the back of a PC) rather than using a USB hub. Clean Software Environment Disable Antivirus