MKV Files not working

I'm hoping that someone can help.

I have been using Serviio for about 3 weeks now and have watched heaps of programs that were an .mkv format, but now for some reason, when I try to play these files I am getting a "This file format is not supported". I then get the message that Serviio is disconnected, and it has to reconnect before I can even access the files. Any ideas?

I'm using the program on my computer, but through a Samsung DVR that connects wirelessly to the network. Everything has been working fine until yesterday.

[Illico]

Please could you provide information about this file (with ffmpeg -i <file> result or MediaInfo result in text format)?
wireless connection is not reliable

[zip]

Check your TV still has the same IP and it's got the right profile assigned to it.