I was starting to panic about engagement because there was a sudden drop off in questions, then I noticed the captcha is not showing and so guests cannot ask questions. Not sure why it has stopped working. Any ideas? The URL is:

http://www.profr.org/homework-help

I have checked the plugin and that is working correctly with the right API codes.
Global joomla config is also set to Captcha - Recaptcha. Confused.