I'm trying to upload a game but all the buttons (such as "upload cover photo" or "upload zip file") are not working. When I click on them, nothing happens and I am not directed to a screen where I can select and upload anything. What's the issue and how do you fix this?

They're not supposed to direct you anywhere, it all happens on the same page. Do you have Javascript disabled, by any chance, or an older browser? Try dragging your files over the respective areas instead.