Well, Tor can be blocked at many places before it ever gets to our website. That's most likely what's happening.
But I have put in a ticket to ask our hosting company about it.
There is a mirror of our website (which is updated only when we do releases), located on GitHub at
https://tunnelblick.github.io. It is generally reasonably up-to-date because we don't usually make a lot of changes to the site except when we do a release. Please report back whether or not that works.