Your installer is outdated, because it's trying to download a version of the main packages that is months old, so they are no longer online. The current version downloads directly 3.4.0.
The installer normally updates itself automatically when it starts, but if your antivirus is blocking the update, you are still stuck with an outdated version that install an older version and will then update it. Which should work normally but not if the same antivirus that is blocking the installer from update itself, is also interfering with the update process which, even if in this case would be longer, should still work.
