Video to Seller- How??

I ordered a pair of shoes in size 8. I was sent a size 11. I sent the seller photos of everything they asked for but now they want a video. DHgate will not let me send videos, and I tried uploading links from Imgur and Dropbox and neither of them worked.

Does anyone know how I can get a video to the seller? Is the seller doing this because they know I can’t send videos and are trying to prevent fixing the problem?