Decided to watch some videos only to end up with no video or a black screen on VLC but the sound was working. The videos worked in other media players.
After trying various solutions online I found one that works.
In VLC go to Tools. Then Preferences. Or use the keyboard shortcut Ctrl + P. Click on the Input / Codecs icon across the top. In the line that says Hardware-accelerated decoding - set to Disable. Then click on Save. I don't know what went wrong, but that's how I got it to work.