Can't run VLC on 10.13.6
I don't have the same issue, but before you try to remove the vlc 3.0.4 and try installing an older version, do you have any errors in the doctor output:

brew doctor
brew cask doctor


If not, then an upgrade, reinstall of the VLC and then force linking the app again might help. Also - if you open the console log when you open the VLC app - can you see any interesting or relevant errors right around when you launch the app?

brew upgrade
brew cleanup
brew cask reinstall vlc
brew link -f


Feel free to @ me in the comments if you make a substantial edit or ask a follow on question to review the output of the above if it's not clear how to fix this once you dig in a bit.