Hey someyousomething , thanks for letting me know! One thing before I report this as a bug - have you already submitted to this exercise before? At the moment we can only store one submission.
Just to add to this, i have found the same problem on a few occasions. How i got around it was to enter something inside the comment field and it works just fine.
Hey, I had sort of the same issue... It seems the submission is not finding my sketchfab account, and I tried to write my account in many ways, even with the other fields filled with some text.