Rated 5 out of 5 stars

This does exactly as it says on the tin. Just be careful that there is a helper application that needs to be installed from the add-on's github page, without it this will not work.

Rated 5 out of 5 stars

Just works!

Rated 1 out of 5 stars

The app does not work

So if you would like it to work, could you please provide more info about what you are encountering, what version of Thunderbird you are using, etc?

Also, did you install the macOS app that is required to communicate between the add on and Things? Information at https://github.com/snchong/thunderthings (which is linked to from the add on page).