@jfn Glad it’s working again (at least for now), but what you’re describing sounds odd. The Firefox extension should be identical in macOS and Windows. Could you post a screenshot of what you see in the Firefox browser extension when you click on the Settings 
button in the lower right corner of the extension window? It should look something like this:
Before posting your screenshot, I would suggest that you obscure your initials shown in the upper right corner, as I have done in the example above.