For Future reference for anyone having same issue, this is the way I fixed it: Clean Cache and then on the website URL of Proko click on the settings of the website, this manages what the website is allowed to do while you are in it (Location, ads etc..). Scroll down to downloads and set the permissions on the box next to "downloads" to "Allow" or "automatically download" instead of "Ask for permission". This makes it so that when you click a file the files they inmidiatly start to download and it doesn't throw you on the error page. The seeting will only affect this website. This will help Mac Users, but I'm sure could work for other systems.