Make sure the USB cable connection between your monitor and Chromebox/Mini PC is tight. When disconnecting the cable, make sure none of the cable's USB port is bent by examining the end of the cable. If any of the cable's USB port is bent or broken, the cable may be defective and should be replaced. Please contact the relevant technical staff.

But...

If the monitor appears to be connected properly, verify the monitor cable is not loose by disconnecting the cable from the back of the monitor and then reconnect the cable. It's is a good idea to rock the cable back and forth to make sure it's not merely loose.

Last, if you still can't solve your problem by using the above-mentioned methods. It's possible that the monitor could be at fault. Please contact the relevant technical staff.