If you still cannot play MKV files using above players, it may be due to the following three reasons:
1. The MKV file is damaged
You can download MediaInfo to check whether the MKV file has video and audio data or not.
2. The MKV file is encrypted
If the MKV file is encrypted, then it may require an appropriate player or permission to play.
3.MKV file is encoded by new video & audio coding
In this case, you need to submit feedback to the official support and wait for further updates or use some audio and video conversion tools to try to transcode.