On the Surface Hub, you may sometimes have to use the "Reset device" feature in the Settings app. Resetting the device is the only way to change its domain membership and administrator accounts. It's also a troubleshooting step for several other driver or operating system–related problems.
After you start the "Reset device" process, do not turn off or unplug the Surface Hub until the process has completed. This may take up to 6 hours. Successful completion returns you to the out-of-box experience, whereas a return to the Welcome screen indicates that the reset encountered a problem and rolled back to the previously existing OS image.
If you see a blank screen for long periods of time during the "Reset device" process, please wait and do not take any action.
Warning: Any interruption of this process can render the Surface Hub unbootable and require warranty service.
Improvements to the reset process are being evaluated and may be included in future cumulative updates.