My Flux XVR / NVR is showing a black screen on the monitor. Stating unsupported video or format.

Most commonly this is caused by the devices resolution being changed to 4K resolution or the Video format swapped from NTSC to PAL.  For newer models you can right click and hold on the mouse connected to the device for 8-10 seconds.  The unit will beep and swap to the next available resolution.  Note this may need to be accomplished a few times before displaying an image again. 

If working with a device that does not support this feature, the easiest fix is to connect the device to a 4K monitor and change the resolution or login to the device over the network and change on the mobile app or within the web client on a PC/Laptop.