BubbleUPnP see but won't play files on Samsung Note 8

I'm a newbie so I apologize if this is covered somewhere and I'm just missing it.

I just installed Serviio on my laptop and can browse and play videos from the MediaBrowser page on the localhost. Everything works fine there.

I installed BubbleUPnP on my Note 8 and can see the server, as well as all my videos. The issue is none of the videos will play. I select one (any) and see it is loaded in the 'Now Playing' tab. At least I see the metadata and the play controls but no image at all. Just the default grey filmstrip graphic. I can click the play button but nothing happens. I installed the MX player app on the phone but that didn't help.

Same story on audio. I can see mp3 files in BubbleUPnP. Can even see the album art, but nothing when I click play.

I realize this is maybe a BubbleUPnP issue since I can play video on the local browser. I can also play videos across the LAN from a PC hitting the MediaBrowser link by IP address.

Any ideas on what I'm doing wrong?

Thanks!