: Users on the Apple Community have found success by selecting Smart Flash in 3uTools and ensuring the "Fix battery health" checkbox is selected before clicking Flash.
If the iPhone's storage was full before the restore, it may trigger this error as it fails to create temporary update files. 3utools error unable to restore idevice75 link
Ensure you are using an Apple-certified (MFi) cable. Third-party cables often fail during high-data tasks like restoring firmware. : Users on the Apple Community have found
If you're still experiencing issues with 3utools, try using iTunes or other tools like Tenorshare ReiBoot, iMyFone Fixppo, or Checkra1n to restore or update your iDevice. 3utools error unable to restore idevice75 link