Thanks for taking the time to report that there is an issue with this addon. Please note, that the Mozilla review system is not meant to be used to report technical issues, see https://addons.mozilla.org/en-US/review_guide. Please use the support site on github to report bugs; not the review system.

Due to the new Firefox WebExtension API, there is something new, see addon description: "Starting with Firefox 57, the addon requires you to install an additional helper application. Otherwise the addon cannot function properly. The details are explained in a first-run dialog when you install the addon."