Can't replicate this, works fine here.
Check all the following:
- You don't have a firewall blocking the download
- The whole Addon manager folder must be added to the Antivirus EXCLUSIONS
- We found some routers having their own antivirus that are also mistakenly blocking the download. Because a user found it and made a proper report, we could identify the faulty antivirus was Trend Micro, used by some Asus router (but not only), so we reported it to Trend Micro, and they reclassified our domain as Safe but, of course, there might be other routers using different software with the same bug, but without knowing what they are, it's impossible to file a complaint with the antivirus vendor.