Playing songs from media server

Hi all.

I am successfully running volumio from my RPI3 with a HiFiBerry DAC Plus. Since I really love the manifest user interface, I decided to become a paying customer a while ago.
Yesterday I connected a USB stick with a bunch of songs I really like and set it up to be a media server. volumio supports this media server and I can browse the songs by folder, genre, … .
This all works, but adding individual songs does not seem to do anything.
When I browse the media server by Folder, for example, and go to a specific folder, I can play all songs in the folder by pressing the “Play” button on the top of the folder. Inspecting this with the browser’s developer tools actually shows traffic happening when pressing that button. However, when clicking an individual song from that list, nothing happens, no network traffic.
I tried this in the app, an Edge browser and Firefox, all the same, doesn’t seem to do anything.
I could be doing it wrong, if so, I sincerely apologise … or maybe it’s a bug … If possible, can someone give me some pointers how I can select individual songs and let them play?