actually, the problem is not in playing the downloaded file because when i turned the media library on, the mkv i downloaded appeared on the list and i got to play it. however, after turning the media library to "off", the list once again did not include the latest download i added. after that, i checked the contents of the hd thru my laptop and the latest downloaded file was there. hence, the media player cannot detect the new download except when turning the media library on (which i do not prefer because it displays all media files it detects in a disorderly manner)