ReCaptcha in joomla contact form AND hikashop

-- url of the page with the problem -- : www.hydrocontrol.org/contact
-- HikaShop version -- : 3.2.1
-- Joomla version -- : 3.8.3
-- PHP version -- : 7.1.12
-- Browser(s) name and version -- : not relevant
-- Error-message(debug-mod must be tuned on) -- : Error
Empty solution not allowed.

Hi,
if I enable ONLY the hikashop recaptcha V2 plugin, recaptcha works as expected, but only in the registration form.
if I enable ONLY the joomla recaptcha plugin, recaptcha works as expected, but only in the joomla contact form.
if I enable both plugins, recaptcha works as expected in the hikashop registration form. However in the contact form, the recaptcha field is not showing. If I click the contact form send button, I get the joomla error message "Error Empty solution not allowed". The form is not sent.

Joomla Global Configuration / site settings / default captcha is set to "captcha - recaptcha". This is also the only available option (except "none", of course)

my question: How do I set up joomla/hikashop, so that I can have a recaptcha check in both the registration form and the contact form at the same time?

EDIT: I just saw the following statement on
www.hikashop.com/support/documentation/7...-with-recaptcha.html
(hikashop recaptcha) will also enable you to add a ReCaptcha anti-spam verification on your contact forms.

So it seems it used to work at some point?

Thank you very much for your help.

Never mind, I found the solution.
- Disable the joomla recapture plugin.
- in the hikashop plugin, enable "use in contact forms"
joomla global configuration / site settings / default captcha is set to none.