Dahua NVR displays "decode not enable" all of a sudden- but didn't make any changes

[jkn]

I have a Dahua NVR5215-16P-4KS2E that has been working flawless since 2018. I have a monitor hooked up by HDMI with several 9 cameras in the split screens. I happened just to click into one of the cameras and then clicked back out to view all the screens again, and not it says "decode not enable". I didn't make any configuration changes, HD are fine, fans are running, I can view all the cameras/playback just fine in the web browser. Seems it's not wanting to display images by HDMI all of a sudden, why is that?

 

[bigredfish]

Assume you did an old fashioned reboot?

 

[jkn]

Yes did a reboot, shutdown, unplugged, plugged in VGA cord and it didn't work. But i did do a restore to default for display with vga plugged in still and it magically fixed itself. Just trying to understand what would have caused it and what does the "decode not enabled" error mean? I assume unable to display camera images to display by either hdmi or vga?