There is also a post on the tech community pages about this issue at the moment with a few people with the same issue, not sure where they are located though, its definitely a known issue but tech support don't know whats causing it yet.
doing investigation with tech yesterday and we discovered the touchscreens I have wont boot up on an Araknis switch or a cisco switch, I was asked to try poe injector the only one i had with me did poe and poe+ and still none of the screens worked. Tech told me that all the units they have received back with this issue would work when plugged into a pakedge SX switch or a "dumb" poe injector so I should try that. I took them home and tried them on a really cheap 48V POE injector and all three worked straight away. it seems to be an issue with the poe negotiation between the midboxes and certain brands of switches/poe injectors. I was told to keep hold of my faulty units for the moment while they figure out where exactly the issue is and what the fix will be, fingers crossed that doesn't take too long.