I have this same problem. It was working great for months, then it stopped working and no one could comment.
I tried clearing caches, didn't work. I reverted to v2/invisible, and it appears to work until you submit, then it always marks it as spam. However, it's worse, because it prevents it from going into the comment queue marked as spam—it just doesn't get submitted at all.
Please help. I'm losing users.
Here's a URL where you can test commenting as a guest by replying to my comment "Testing comment logged in."
