A firmware update was recently released for the NVR6XX-4KS2 series devices.
Information, instructions, and download links can be found Here
From Dahua Wiki
After I connected to the IP channel, there multiple*window output is OK, but there is no one*window output.
There are following possibilities:
- Check there is video from the IP channel or not. Please go to the main menu*>info*>System*>BPS to view bit stream real*time information.
- Check the main stream of the camera has been enabled or not.
- Check the main stream type of the camera is H.264 or not.
- Check the device supports camera main stream resolution or not (such as 960H, D1, HD1 and etc.).
- Check camera network transmission has reached the threshold or not. Please check the online user of the camera.