Follow the steps listed above for Error 1604. Also, discard the .ipsw file, open iTunes and attempt to download the update again. See the steps under Advanced Steps > Rename, move, or delete the iOS software file (.ipsw) below for file locations. If you do not want to remove the IPSW in the original user, try restoring in a new administrator user. If the issue remains, Eliminate third-party security software conflicts.
This error is often related to USB timing. Try changing USB ports, using a different dock connector to USB cable, and other available USB troubleshooting steps (troubleshooting USB connections. If you are using a dock, bypass it and connect directly to the white Apple USB dock connector cable. If the issue persists on a known-good computer, the device may need service.
If the issue is not resolved by USB isolation troubleshooting, and another computer is not available, try these steps to resolve the issue:
- Connect the device to iTunes, confirm that the device is in Recovery Mode. If it's not in Recovery Mode, put it into Recovery Mode.
- Restore and wait for the error.
- When prompted, click OK.
- Close and reopen iTunes while the device remains connected.
- The device should now be recognized in Recovery Mode again.
- Try to restore again.
If the steps above do not resolve the issue, try restoring using a known-good USB cable, computer, and network connection.