Your customers receive an error message "unable to verify the first certificate" when they try to submit an aggregated review form.
This error occurs when an SSL certificate on your website is not properly configured. When a customer submits a review form, AWS (Amazon Web Services) server hosting this review form tries to transmit customer reviews to your WooCommerce site. If it cannot verify SSL certificate of your website and establish a secure connection, this error will be displayed.
Please check configuration of the SSL certificate on your website. For example, you can use this service: https://www.ssllabs.com/ssltest/index.html. It is likely that some intermediate or root certificates are missing.
After you fix the problems with SSL configuration, try submitting a review form again to verify that everything works correctly and your website is able to receive customer reviews.