Adobe Document Cloud - Upload Error: an error has occurred

When uploading a document to Adobe Document Cloud to send for a signature, i get an arror message "Upload Error: an error has occurred". I'm using Windows 10, Internet Explorer 11. I've tried to upload two other documents that ive successfully uploaded to Adobe Document Cloud before, but they too have failed. I've also tried uploading directly from Adobe Acrobat XI, but that just hangs. What can I do? I cannot send my contracts to my clients.