Playback from LMS server fails

I am running Volumio 2.457 on a Pi 3B+.

I have an external hard drive of music in a powered case.

Volumio plays from that HD fine when it is plugged into the pi running volumio via the usb.

I have another pi serving as an LMS server, when I plug that exernal drive into the LMS server, my Squeezebox plays off it just fine.

If I go to “browse -> media servers”, then the volumio will find that LMS server, and all the music on that drive.

But when I try to play music from the harddrive via the LMS server, I get a little popup saying that it is now playing the song, but I get no playback, and no progress through the song. I get no “pause” button appearing, the “play” arrow remains on the interface.

I am stumped, what should I try to do to figure out what is going wrong here?

TIA.