I confirm this appears to be a bug. Captcha works for ‘Google reCaptcha for questions’ but it does not work for sign-up. You can actually see the captcha box when asking a question but you cannot see a captcha box when signing up.
Please never ever send your personal information through other communication channels such as Skype or personal email addresses not from enginethemes.com.
Should you have any question or need help with your website, please contact us via Ticket System or firstname.lastname@example.org.