This warning message indicates that the AVCAPublish service is not running. This service is responsible for a number of background tasks, and must be running in order for AV Capture to perform critical functions.
The AVCAPublish service is designed to start automatically when Windows boots up, but with a built-in delay. Launching AVC prior to this will trigger the warning message. Therefore, it is best practice to always wait a few minutes after Windows boots up prior to launching AVC.
When encountering this error, the best course of action is to close AVC, wait a minute or two, and relaunch AVC. If the error still occurs, we recommend either manually starting the service, or rebooting the PC.