Sony BDP-S580 will not recognize .mkv files

I am new at this and wonder why my BDP-S580 will not play .mkv files I have in my serviio library. Avi's, mp4's and ts files play just fine. Is there a newer profile I should be using instead of the Sony DBP-Sx80/SMP-200 2011 that I am using?
All I do is store my movies on my PC HD AND Use Serviio as my DLNA server.

Thank You