Problem Description:

This error is typically caused by attempts to downgrade the iPhone, iPad, or iPod touch’s software. This can occur when you attempt to restore using an older .ipsw file. Downgrading to a previous version is not supported. To resolve this issue, attempt to restore with the latest iPhone, iPad, or iPod touch software available from Apple. This error can also occur when an unauthorized modification of the iOS has occurred and you are now trying to restore to an authorized, default state. Very rarely this error is caused by a hardware issue and requires service.

Solutions:

Step1: Set your iDevice into DFU mode.

•  Hold Home button and Power button simultaneously for 10 seconds till the screen becomes black, and then release Power button. 

• Continue pressing Home button for fifteen seconds. You’ve successfully set iDevice into DFU mode if you can see an iTunes logo on iDevice’s screen.

Click to enter DFU mode and Recovery Mode

Step2：Launch 3uTools. After connecting iDevice to PC using the USB cable, 3uTools can check this iDevice in DFU mode automatically.

You’re suggested to back up this iDevice using 3uTools first. Choose an available firmware and click Go Flash to restore your iPhone. 

Then please keep a good network connection between iDevice and PC, and then wait until this process is completed. 

You could check here for more error codes roundup in 3uTools/iTunes.