If you find all cameras' image disappears on TV frequently, please try methods below.
1. Please unplug your NVR from power source and plug it into power source again to reboot system.
This method is effective to solve image disappearance problem.
2. Please disconnect NVR from router to see if problem can be solved.
3. When camera's image is not shown on TV, please go to setting to see if NVR can detect camera's IP. If yes, you add camera to NVR manually to show image.
Here is instruction.
4. Please go to main menu--advanced--restore to select all to restore system to have a try.
If none of above methods work, please contact email@example.com for further help.