Plex & DLNA

I've had the Marketplace App Plex Media Server running for a while and connected to my NAS.

I can use the web interface to play movies, tv & music, but I'm not able to connect via DLNA.

I haven't changed the default settings on the Plex server advanced DLNA.

For example. Both my Bose SoundLink/SoundTouch & VLC Player will show the Plex Media Server:PlexMedia in the UPnP but I can't connect. In VLC Player there is a yellow triangle with !. I can't find out what that is supposed to mean.

I'm sure I've missed some set-up step somewhere along the way.

What I should be checking?