McAfee web advisor
I installed mcafee web advisor and it doesn't show up in the add-ons or extensions. This was working in the past, I believe, but it doesn't show up now.
You should contact McAfee support.
Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)
In the Add-ons Manager, on the left, select Extensions. Is the add-on turned on? Any error messages?