dear @sbelew, this could be for a multiple reasons, and one of those is that the system at that time it was down. In your case I would try again but before clearing all your browsing history on the search engine you are using within your organization. Of course I also assume you were only try to upload PDF or pictures as receipts.
Please re-try or provide a more detailed situation of what were you trying to do with screenshots and when the error happened.
@sbelew is this issue still happening?