DLNA codec not compatible? watching movies on TV from mycloud

I have a MyCloud Mirror and I connected my Vizio TV to my router by ethernet directly. Under multimedia, MyCloud shows up with a list of videos, but when I try to play, it tells me the codec is not compatible, or something to that effect.
My movies are on a USB drive connected to the MyCloud and are all in M4V format.
Any suggestions on how to remedy this? I can’t find any info anywhere.

This YT video may give you some clues https://www.youtube.com/watch?v=g9Zj1q0eEvU

Thanks longedge. That was helpful and it made me think a little more about how to solve this. I ended up discovering that Roku has a media player app. It recognized MyCloud fine, and played the movies with no problem, whether they were m4v or mp4.