Ok. Try this.

1. Unplug your phone. Plug it in. I tried this several times and got it to work on the 10th try. It's weird.

2. On your phone, go to settings, connections, usb to pc, and uncheck Advanced Networking.

3. Worse comes to worse uninstall the Mobile Device center and re-install.

4. Don't give up. It eventually comes up. Mine took about 15 minutes of tinkering.