Rated 4 out of 5 stars

I was able to fix the suggestion pop-up using this:
https://github.com/alainfrisch/nostalgy/issues/10#issuecomment-99588036

* Make the Thunderbird window less high by dragging the window smaller from the bottom of the window
* Hit "g" and type something
* Quit Thunderbird
* Start Thunderbird
* Now it works (even after a restart and resizing the window again)

This review is for a previous version of the add-on (0.2.33).