This one has many hundred discussions. Let's cover (repeat) the basics fast. MKV is a container so what's inside has to be encoded in what works. While there is a list in the manual since MKV is a container and not an encoding we can't write all MKVs will play. It is true that units can see into the MKV but encoding is another matter altogether.
Try other encodings and updates tend to be something we can't count on.
I own a 3D blue-ray player BD-C6900 from Samsung. I have made the last firmware update yesterday. (BSP-C6900WWB-1020.4)
Since then, my BD-C6900 player is not able to play .MKV files anymore. (Matroska Codec)
It was working well with .MKV files, until I made this firmware update. Almost all my video files are encoded in .MKV codec. I've call Samsung support center 2 times and they told me it was impossible to downgrade my BD-C6900 firmware. They also tell me they had no idea how to fix it. I'm still able to play .AVI and .MP4 files. I've try every way to play these files with usb external drives, with Samsung PC Share Manager and even with a DVD disk with .MKV files on it. I also tried to format a usb key and still not working with .MKV video files.
80% of my video collection is in .mkv so it's really annoying ! I got the error message : "this video codec is not supported" But it was working fine with the old firmware .. I really do not understand why they make firmware updates to fixes something and create other issues ?
If you guys have any clues about this issue just tell me or maybe I'll have to wait until the next firmware update to see if they fix that problem.
Thanks for your time !