Mini M4 and Cinema HD not working

Help. I have a Mini M4 and a Cinema HD display, and they don't like each other. The display worked fine with my Intel Mini, and the DVI to HDMI adapter also worked. When I connected the HDMI to the M4, no display. I connected my TV via HDMI and got a USB-C to HDMI adapter from apple for the Cinema display, and still nothing. I can see the screen change from black to dark grey when I plug it in, and the Mini shows a second display in settings, but I cannot get anything to show on screen.

Any suggestions are welcome.