Captcha answer is missing

Just finished implementing the OS servicebooking plugin. So far everything went smooth, but on submitting the form I keep getting the following error:

0Captcha answer is missing. Note that JavaScript is required to submit the form.
I'm using Google reCaptcha V3 (invisible) which works on the normal contact form, but somehow gives an error here. 
Any Ideas on what is wrong and how to fix it?
 

Hi Susan,
If you are using Joomla 4++, you won't able to use Google reCaptcha anymore, because Joomla doesn't support Google reCaptcha from Joomla 4.
You can submit ticket on category: OS Services Booking, and i will send you JD Captcha plugin, and you can use it with any extensions of us.
Thanks
Dam