If you are using EpocCam Viewer it can only display video stream on screen.
To use EpocCam as a camera inside other applications, you need to download our plugin for macOS. For the plugin to work correctly you also need to quit EpocCam Viewer.
Please note that the plugin only connects to your iPhone when an application is using the EpocCam camera plugin.
This behavior is different in Windows, where the driver automatically connects to the iPhone app, even if no application is using the EpocCam camera plugin.