Are you using a Chrome (based) browser by any chance? This happened to me (Opera on a Mac) today. Instead I grabbed the URL and used wget in a terminal window and it worked like a charm. If you’re on windows try using FileZilla, or anything except the browser.
I checked the connections on the LM2596, and re-soldered just in case, but no change. I’ve contacted OpenLab, and they’ve said they will sort something out. Many thanks for your help.