There is a known issue in VLC 3.0.6 which causes the video to only show a black screen. This is caused by a bug in the WEBM decoder that causes it to fail if it uses multiple cores. To fix it:

• Go to the Tools menu in VLC
• Select Preferences
• Select All instead of simple in the bottom left corner
• In the tree view, select Input/codecs, Video codecs, ffmpeg
• On the right, in the decoding section set threads to 1