I had the same issue and following the advice on this guy’s blog post fixed it for me. The key for me was the version of reCaptcha that I needed to use as each version has different SPAM settings.
I was having this exact same issue and posted here on this forum. All the developer told me here was to “read the FAQ,” which wasn’t helpful at all. I finally was able to fix this problem on my site by following the instructions in this blog post here:
Thank you! I was able to post using that link you gave me. Interesting is that I still can’t post to that forum if I were to go to the forum itself and try and post not using the link you provided.