An Evernote contact spent an hour with me and took over my computer with my permission. She could not fix the problem. She said that I would have to create another Firefox Profile. The one I have is broken or corrupted. Here's a note from our session: Here are the steps to create a new Firefox profile, if you would like to give that a try: 1) Open Firefox profiles page (copy and paste about:profiles to the URL address bar). 2) Find a profile with a label "This is the profile in use and it cannot be deleted" and remember it. 3) Create new profile with any name and location by default. 4) Set new profile as default profile: the image that evidently can't be copied and pasted here states: "Profile: TEST NEW PROFILE, Default Profile yes" 5) Restart Firefox. 6) Install Evernote Clipper 7) Click on Web Clipper icon and check if Clipper menu opens and article is clipped If this procedure helps, the main reason is a corrupted initial Firefox profile (where the Clipper issue happens.) If this is the case, I recommend using the new profile you just created. To return to the initial profile, set as default the profile from the step 2 and restart Firefox. For more information about Firefox Profile Manager, click here. If this workaround doesn't resolve the issue, please contact Firefox support. I'm afraid I don't have more information about the Firefox profile setup on your Mac. I did not try that. Thought I'd go to the Firefox experts first!