Here are a couple of starting points that you can check in case you are having issues with outputting video from the V-1200HD:

Is copyright-protected (HDCP) video being output?
Check whether an HDCP-compatible monitor is being used

Does the output-destination device (HDMI monitor, etc.) support the output setting specified on the V-1200HD?
On the V-1200HD, video in the same format as the process format set for the respective process is output. For instance, if the process format for the 4:4:4 process is set to 1080/59.94p and video is output from the HDMI OUT 1 connector, video output is possible if the output-destination device (HDMI monitor, etc.) supports a 1080/59.94p signal.

Are the patchbay settings correct?
Use an optional V-1200HDR unit or remote-control software to change the patchbay settings.