Are you using a PC running MC as a DLNA Server and DLNA Controller, and the nVidia Shield as a DLNA Renderer?
That is, JRiver for Android running on the nVidia Shield hasn't loaded the Library running on the PC, so it isn't running as a MC Client, correct?
So you are pushing media from the PC to the nVidia Shield, and not using the JRiver for Android on the nVidia Shield to Pull media from the PC?
You're selecting the nVidia Shield as the Zone in MC on the PC?
You're selecting a media file in MC on the PC, and selecting Play?
I just did this to play an MP4 video on my Sony Xperia, which runs the Mobile version of JRiver for Android. It played fine, although once started the Stop button on the PC couldn't stop playback. So there is some control issue.
For Audio, playback and the Stop button worked fine.
If I load the Library from the MC Server running on my PC into JRiver for Android on the Xperia, I can't get the video file to play. Both MC on the PC and JRiver for Android on the Xperia show that they are trying to play, as seen in the Media Network Service on the PC, but the GET command doesn't actually get any data, and there is no Playback command. I have a DLNA Server associated with the Xperia and tried changing video conversion settings, not that they should work, as they aren't Client settings, and should only work when connecting the Xperia as a DLNA Renderer and not a MC Client, but I thought I would try. That didn't work.
Audio played back fine with this connection configuration. i.e. The PC Library loaded on the Xperia.
I didn't get any messages regarding Controlling the DLNA device.
So what are you sending to the Shield, and how are you sending it?
As above, I'm using JRiver for Android Mobile version 26.0.29.