Rated 3 out of 5 stars

When I click "install in Thunderbird" nothing happens
No error, but no add-on in the installed list as well

This review is for a previous version of the add-on (3.5.1). 

That sounds like an addons site problem, but I can maybe help pin it down if you email me. Please raise issues via github, though, and not the ratings mechanism, I don't always see these.