If you use Linux or Mac look here:
> For MacOS & Linux users: Use left or middle mouse button due to the different right click/context menu behaviour (see this bug ( https://bugzilla.mozilla.org/show_bug.cgi?id=1360278 ))

Does it only work on certain pages like about:addon or newtab? Then look here:
> The addon does not work on https://addons.mozilla.org, pure svg pages and internal pages like about:newtab, about:addons or other addon option pages.
And here: https://github.com/Robbendebiene/Gesturefy/issues/6