Rated 5 out of 5 stars

Από τον/την Χρήστης Firefox afa19a στις Δεκ. 5, 2017 · μόνιμος σύνδεσμος

Due to changes in the Firefox API, this add-on cannot be made compatible anymore for Firefox 57 and above. Best alternative is to reinstall Firefox 56 and to disable automatic updates.

https://www.wikihow.com/Downgrade-Firefox