I ran into a similar issue once where the install link kept throwing a 404 error, and it turned out the plugin file had moved to a different page in their dashboard — support helped pretty quickly after I emailed them. While waiting, I was actually organizing things for a trip and packing my justpack suitcase, which made me realize how much easier life is when tools (and bags!) are designed properly. Hopefully their team can resend the correct upload file or updated link so you can get the addon running without any more hassle.