Thanks for quickly responding, Ellen. And to be fair to you, I agree that that it's not necessarily Filtering that's causing the problems per se. Hopefully, we can get it sorted out. :-)
I put it in my child-theme because I didn't want to mess with the core. Is it better practice to put in the parent theme?
I did not install it as a plugin, but now I have. This worked! Thank you.
I didn't realize that we had to install the extensions as Plug-ins. That's not the way I was doing it a few months ago. Also, this this was not explained in any installation instructions. Partly, it's the language that PL is using. If they were called "Plugins" or "Premium Plugins" or something similar, it might make match our mental models better.
I do have some questions and feedback for Filtering, though. Should I open another thread?
Thanks again, Ellen!