Just tried to download this myself and found the exact same problem using Firefox on Gentoo Linuxand, like mcandre says, i've not had this issue elsewhere . Will try other browsers and see if I get the same result...
...Yep, can confirm that I have the same issue in Vivaldi, Opera and SeaMonkey. However, as suggested, I can download it from the My Purchases page just fine. Bit odd but at least it's not a show-stopper.