Can you check with pavucontrol-qt (KDE-only; use pavucontrol-gtk, if you’re using Gnome) whether your VLC audio stream is visible to PulseAudio?
In KDE/Plasma 5 you also can use the volume widget near one of the desktop corners; keep an audio file playing in VLC while checking — VLC should then get listed in the »Applications« tab in that widget.
I’ve also found the following articles helpful to fix audio issues:
- https://en.opensuse.org/SDB:Audio_troubleshooting
- https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting
Hope this helps.