Some videos on facebook not working

I'm using a Lenovo laptop, Windows 10. When using any of my browsers (chrome, IE, Edge), FB will automatically play some videos,but refuses to play others. It opens a window with page blacked out. If I press to see the next vid, I get a message saying there is a problem playing the video. I have enabled all players, unchecked hardware acceleration, deleted all caches, updated all players, deleted and re-installed all browsers, updated intel drivers, and so on and so on. I've followed loads of posts on here, to no avail. This started a couple of weeks ago and it's driving me mad! All other sites work perfectly and there is nothing on FB to help (waste of time). Please help!!!