Unable to respond in dispute

[sarahbarbour]

A client claims I didn't send him the work he asked for (I did) and canceled the job, which I am disputing. When I try to respond to his claims and keep the dispute open, I get the following message: "We are experiencing a technical problem and cannot process your request right now. Please try again in a minute." 

I've tried multiple times, refreshed the browser—I do not want to let this dispute close for lack of response. Can anyone help?

[sarahbarbour]

I guess the issue was that I was trying to upload a file as well to prove that the work was done. When I stopped trying to attach the file, I was able to post.

I've never had a client respond negatively to work I've done, so I'm a little at sea here. If anyone has any advice, please let me know.