As I recall, sometimes with HDMI based devices, there can be compatibility issues due to the copy protection part not being correctly handled — that is, one device does not think the other device is “legal” and will refuse to work.
Normally this does not happen with cameras and monitors, but for devices where it does, a lot of times, it takes trying several different cables to get things to work. I am not sure why the cable usually is at fault, but swapping it may reset the protection circuitry.
How have you tried making sure the new monitor correctly works?
Connect it to a blu-ray player or some other device that can output video over a HDMI cable and make certain the monitor is okay.
Try a new / different HDMI cable from the camera to the monitor.
Try different video out settings.
p.s. Welcome to the forum.
