Puntuado con 4 de 5 estrellas

The development version of the plugin available at the below URL fixed this issue for me. It appears the author is aware of the issue and will be updating the plugin hosted here shortly.

Development version (1.3.6bxxx): http://ajnasz.hu/files/dev/grwatcher.xpi

Esta valoración es de una versión anterior del complemento (1.3.5.1-signed.1-signed). 

Fix for no icon showing Puntuado con 4 de 5 estrellas

To fix the no icon issue, uninstall the addon, restart firefox completely, reinstall the addon. At least in my case, it brought back the missing icon and all is good in the world again!

Esta valoración es de una versión anterior del complemento (1.3.5.1-signed.1-signed).