fresh install of 18.04 after completely purging 16.04. Aplay plays audio. Sound test in sound settings works. system sounds work but browser sound and vlc/video player gives no sound output. edit : it was working till just before i plugged in hdmi to play on tv
Try to walk through Sound troubleshooting procedure . I'd try step 6 first. Install
pavucontrol and look maybe you have some applications muted. Also try changing audio device back and forth.