I'm not sure if it still works; but I was able to, even with the errors.
See here: construct.net/en/forum/scirra-website/website-issues-and-feedback-35/my-game-is-not-being-uploaded-136428
Also don't forget to cut out your screenshots.. your whole Windows 10 bar and browser tabs are visible on the screenshot. It's just good practise.
By the way, a new Arcade is supposed to be in the works, or at least I think they said so. Not sure what the hold up is though.