Input cables connected right ?
Input cables connected right ?Volume at min. Or on Mute.
Input signal connected right?In VGA mode，The PC refresh rate ＞75HzIn VGA mode，The PC contrast ratio is ＞1024*768
Re-plug the deviceCheck if the device is broken.
The format of the video is right ?
Files is broken ?
Device is broken ?
The decode system doesn't match.