My Ultimate+ has a black screen and will not turn on or off, but still outputs powerUpdated a year ago

Your Ultimate is most likely in lock mode. This feature prevents the screen from displaying anything, and will not allow any button presses while still outputting power.

To enable lock mode, make sure your Ultimate is powered on and hold down the AC output button for 5 seconds.

To disable lock mode, hold down the AC output button for 5 seconds.