Screen-share is just a black video
When screen-sharing, your local preview and output is black
Google Chrome's HWA setting
If the video preview when screen sharing is black, try disabling or enabling the browser's hardware acceleration. This can be found in the Google settings -> system menu.
If sharing a Netflix, Prime Video, or other content that is protected by content-protection, such as DRM/HDCP, the screen share may be black also. You can try screen sharing using the window, display, or tab methods to see if one works where the others fail, or you can try display grabbing with OBS Studio instead, but VDO.Ninja itself doesn't offer methods intended to bypass content copy protection.