I have 3 Rpi3+ each running Volumio, latest version, and they all run into the same issue.
I’ve never had a problem loading the interface. However, once the interface is loaded, the play button either switches to a pause button and appears to be playing with no sound output, or the play button doesn’t change to a pause button, yet a notification that Volumio has started playing flashes in the upper right.
If I unplug the 3.5 from the headphone jack, and plug it into a different mixer input, does this trigger something in Volumio to kill the audio until I re-boot?