Great that you've found the problem. We may adapt our extension to support multiple categories in some future version.

I have realized that ever since I got the URLs to work, the Google links have not been updated. What could block that ? Are there specific configuration issues that I should be careful with, that could block Google from being able to update the site references ?

I'm not aware of any configuration that could affect this. It can take quite some time (even few weeks) for Google to update the links.