Ajax submission doesn’t work

We were having an issue with the forms not submitting. None of the posted solutions worked, including creating a new simple form or using the Enter key instead of clicking the button with a mouse.

This problem came up after migrating to a new server with PHP 7.3 (php-fpm) and NGINX (instead of Apache). Not sure if those are factors or if there is a permission issue. I can’t find any errors in the logs or in the console.

Afterwards I found an article about Ajax Load. I was able to get the forms to work on a temporary basis by disabling Ajax Load in wp-contact-form-7.php:

if ( ! defined( 'WPCF7_LOAD_JS' ) ) {
	define( 'WPCF7_LOAD_JS', false );
}

We would prefer to use Ajax for form submission, so any help would be appreciated.

The page I need help with: [log in to see the link]