Error 0xE8000015 when you try to connect ipad to iTunes.

Today my colleague forgot the passcode of an ipadmini device.

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled. You have to connect the iPadmini device to iTunes on the desktop in order to restore the iPadmini to the factory default. (refer to https://support.apple.com/en-us/HT201413)

However when I plugged the iPadmini to the usb port of the desktop and opened the iTunes, my iTunes showed ".......Error 0xE8000015...."

I couldn't solve the problem after many trial.....unplugged the iPadmini, turned off the computer, removed the iTunes, the related apple software and downloaded again, tried to connect to the other computer.......still failed...failed....failed to get the iPadmini connected to iTunes. 

When I got home from work, I didn't give up trying to connect to my laptop. I thought it could be the version of iTunes which caused the disconnection. After connecting to iTunes, the problem was the same. I tried to search for the solution again. This time, I found a way to " press the HOME button and the POWER button until the apple logo on the screen, then let go the POWER button until 

After this trial, the iPadmini connected successfully to iTunes, but would get stuck or failed before the completion. Suddenly I found my desktop and the ipadmini connected to the different network(subnet). Then I switched the desktop to the wifi mode and connected to the same subnet of ipadmini. "BINGO"  

Then the ipadmini connected to iTunes and the restore went successfully.