unfortunately, Firefox automatically disabled it this morning and it is impossible to download it again: "Download failed. Please check your connection"
Updated: extensions should be working again: https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/ ... thanks for updating your review!
This is a problem on Mozilla's end; they are working hard to fix it right now. https://bugzilla.mozilla.org/show_bug.cgi?id=1548973
