The file is the same as all of the other files, jpeg. I will leave this on here until you look at it, let me know. Like I said, I have never had problems before. Let me try another one and see if it works.
Edit: Well, apparently, it was just that one screenshot, so I don't know why it didn't take that one. I tried a couple of different ones and they went in fine, oh well. No worries. Just pretend you didn't see this post, lol.