Volumio as UPnP server, why is Volumio: root empty?

I am new to Volumio and installed 1.4

I would like to use Volumio via DLNA. I have a PI. So setting up was easy, my files are on usb and they are in the volumio library.

Yet when I choose volumio:root on plugplay on iPhone all folders are empty.

Is there anything else I have to set up, so Volumio will also work as a UPNP server?

How do I get my files to show up in the Volumio root folders?

Is Volumio supposed to work as Server and client?

if you want to play music from your usb stick pluged into your rapsberry you can do this with the web interface or with a mpd app

if you want to play music from your smartphone you can use upnp

(try the upnp indexing in the volumio settings)