Hey @Jen,
I’m sorry to hear about this issue on your site! The captcha is working for me on my testing site, and in searching for similar issues to this I wasn’t able to find anything; so, unfortunately, this may be an issue unique to your server or something.
To get started on trying to figure out if that’s case: how are you hosting your website? E.g. are you self-hosting somewhere, are you using something like GoDaddy web hosting, or Media Temple, Pantheon, WP Engine, etc.?
Next, can you share your System Information with us? Here’s how to do so → https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Finally, to clarify: does this “internal error” show up just when you go to the page itself? Or does it only happen when you try submitting the event there? And in either case: does the whole issue go away if you simply remove your Captcha API keys?
Thank you!
George