Please check following preferences in about:config page: extensions.rightlinks.enabled extensions.rightlinks.enabled.left Both should be "true". (Or open Add-ons Manager, navigate to Right Links and click on "Options…" button – should be checked "Enabled" and "Options – Enable long left-click")
If still doesn't work, please provide detailed report here https://github.com/Infocatcher/Right_Links/issues or here http://forums.mozillazine.org/viewtopic.php?f=48&t=645809
Also please try install Right Links on new profile: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles And if it works on new profile, this is probably conflict with other extension or non-standard configuration. And I need information from about:support page.