Yes, I was able to register with my Gmail account, validate the registration, and login without any issues.
I don't think that a privacy plug-in, or tracking protection settings in browser, would break stop forum spam as it's done via a connection from your server to their server.
I'm wondering if there was some hiccup between your server and stop forum spam when you were testing, when you access the settings page in the control panel what does the service say when you click test connection?
