Video [Q] Default video player wont change

First of all I'm sorry if I'm posting in the wrong forum. I'm posting for the first time.

So I watch alot of video which are being posted on Facebook through my mobile using MX Player or download them using Easy downloader. By about a week ago it stopped working. I mean like I can only play videos through default video player. I tried changing the default video playing app and everything but still no luck. i even changed ROMs but still the same.

All I wanna do is watch videos on MX player or download them using easy download. Please help me with this.

Thanks in advance !