VIZIO P Series App - No DTS Passthrough

I recently purchased the new Vizio P 70" TV and was elated to find it had native PLEX support built in. Finding the media server was easy enough and playing content does work, but PLEX is not passing DTS audio down the ARC to my receiver. The system seems to be capable as playing the same file through Vizio's built in multimedia app via DLNA (from pms) does pass the glorious DTS signal through to my receiver. 

Thanks for your thoughts and suggestions!