Videos unable to be played on whatsapp or my phone

So the last month or two a lot of videos i download from discord that i want to share with my whatsapp group cannot be played on my phone or on whatsapp. 
it says "preview unavailable" before the upload. and after the upload you can't play it. 
I'm forced to use https://cloudconvert.com/ to convert the mp4 i download from discord into mp4 there for them to work properly again. an example of a video that won't work: 
https://cdn.discordapp.com/attachments/669158942139613186/1047942604261699695/8669321407562608431.mp4