If only audio plays, use a converter like Handbrake to change the container to MP4, or update your media codecs.
I can give you a specific solution, such as recommending a converter or the best player to use. download large mkv files with php script - Stack Overflow Download File NuHoangThamVong_02.mkv
Likely a file-sharing service or messaging app like Telegram. If only audio plays, use a converter like
VLC Media Player (best for Windows/Mac/Linux). Alternative: DivX Player. If only audio plays