Why don't you remove it and install it back in again.

Make sure Firefox isn't set to run in permanent Private Browsing mode (Always use Private Browsing mode; Never Remember History) as not all extension may run in PB mode. *https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history *https://support.mozilla.org/en-US/kb/extensions-private-browsing *Settings -> Privacy & Security<br>Firefox will: "Use custom settings for history" *remove checkmark: [ ] "Always use Private Browsing mode" ---- See also: *https://support.mozilla.org/en-US/kb/extensions-button