Hi,
As far as I can see, the Recaptcha is working fine on your website.
Note that captcha can be easily circumvented by bots nowadays.
If you want a better protection, I would recommend other kinds of anti bot protections.
A solution like this is probably more effective and can complement the recaptcha plugin:
www.joomlashack.com/joomla-extensions/ospam-a-not/
This plugin works for both Joomla and HikaShop and is free.
Finally, another solution is this :
extensions.joomla.org/extension/access-a.../easycalccheck-plus/
This integrate with 3rd party services to check if the email address being used has already been flagged as fake and if so, it directly cancel the registration. This works for Joomla, HikaShop, etc, any extension with registration on a Joomla website.