Here is a guide to diagnosing and fixing this issue.
If you must use Overlay Mixer, ensure your graphics card's hardware acceleration is set to "Full." You can find this in your Display Adapter Properties walaoke problem with overlay mixer verified
: Traditional Overlay Mixers typically only support one video stream at a time. If another program (like a web browser or media player) is using the overlay, Walaoke will show a black screen or an error. Secondary Display Issues Here is a guide to diagnosing and fixing this issue