I'm really sorry I missed your last comment!
I've personally been using Ren'Py 8 ever since the launch of this tool, but I downloaded 7.8.7 to test this, and I got it to work just fine in a fresh test project.
To make absolutely sure, is your wordcounter file inside of your project's game/ folder? (A screenshot of how your folder structure is set up might also help.)
I'll also admit Ren'Py not respecting your "character counts by speaking character" setting is very strange. Does it only do that if the wordcounter is there, or in general?