ramesesjd Can you check if it works fine trough headphone jack? I'm not sure if audio passtrough settings have any effect here, but make sure that audio passtrough is disabled. If it works trough headphones and audio passtrough is disabled, then it's possible you have same issue as it was already reported here. I don't know how to fix it as I don't have any issues with HDMI audio on any of my devices.
I tried this, but the sound is the same coming through the headphone jack, however I don't have any option to enable or disable audio passthrough. There is nothing displayed below 'Audio Passtrhough' on the Settings/System menu.
EDIT: Like @andre_726, I have a Samsung TV that my Pine A64+ is connected to via HDMI. Unlike that user, though, I am able to get audio from all sources besides Spotify. Unfortunately I don't have another HDMI screen to see if this is only a problem on this particular make/model.
Cheers
-R