In this situation when your pen display is plugged in you may see something shone on the screen for a moment and then nothing is shown on the screen for a moment and then it cycles and shows you something on the screen again. This cycling we'll go on forever.
When it is on you may see that the screen is just showing a field of a solid white color. Or you may see a brand logo or some other indication that the display panel is actually working.
Overwhelmingly the primary cause of this cycling seems to be that the pen display is not getting enough power.
If you're connecting through a three in one cable. Please make sure that the power is coming from an AC adapter instead of from a computer. Often computers can't deliver enough power especially when the pen display is larger than 13 inches.
If you are connecting via USB C cable, then try a different port because maybe it will supply enough power. Or you may have to switch to using a three in one cable.
In at least one case I've encountered a situation where someone's pent up but performs this cycling but it is not due to being underpowered. In this case it had to deal with how warm the pen display was getting due to the current weather conditions.
Here is the thread from Reddit which describes this case.
https://www.reddit.com/r/huion/comments/1fzfihm/help_kamvas_13_turning_on_and_off_repeatedly/