Puntuado con 1 de 5 estrellas

as the last review, just works for ONE time.
then restart the browser to use again.
I am on linux

Esta valoración es de una versión anterior del complemento (1.0.1-signed). 

I'm on Linux too. As a Linux user, when reporting a bug, I typically find it more beneficial to getting quality report when I say what version of Linux and what versions of other stuff (such as what version of Firefox you're using.)

Also, a step-by-step with links would been incredibly useful. If I can spend 20 fewer minutes trying to reproduce the issue, that's 20 more minutes I can spend fixing the issue.

But I've already invested/wasted those 20 minutes reproducing the issue, and I can see it now. I'll post an update once it is resolved.

This issue is being tracked at https://github.com/ecaron/firefox-font-fonder/issues/1