Vivotek ND9541P User Manual page 44

VIVOTEK - Built with Reliability
5. Why live view is unavailable?
The default live view receives a camera's stream #1. If a camera's stream #1 is configured using
MPEG-4 as the video codec, the following message will prompt.
You can go to the Settings > Camera > Media > Video window to configure the video codec of
stream #1 into H.264 or H.265.
44 - User's Manual