This is caused by resolution compatibility issue.
The default output resolution of the NVR is 1280*1024, which may not be compatible with some screens.
Here is how to solve it:
- Connect the NVR to any other screen via VGA; (or you may also try any other screen via HDMI to see if you can enter the menu)
- When you are able to see the menu, click right button on mouse, go to System Setup – General Setup – Screen Setup – VGA resolution; change it to 1080p@60; apply to save it.
- Connect it back your primary screen via HDMI. You should have it worked with the screen.