I know that this is a dying forum. But this is my last ditch effort.
I have a ZTE Axon M and was as the subject said, the second screen has no display. The touch and 'M' button works with the dual screen, mirror and expand mode yet all blank and responsive to touch.
I know the touch works because when I use mirror mode, and touch on the same reference place on the second, black, blank screen, the touch response works.
Thank in advance.
PS. I find this phone quirky and unusual - my type of tech.