Error with payment request button

Thank you for reply!
I disabled plugins and tried the shortcode in a static page, but still got the same error until I added this code to functions.php

add_action('wp_head', 'myplugin_ajaxurl');

function myplugin_ajaxurl() {
    echo '<script type="text/javascript">
           var ajaxurl = "' . admin_url('admin-ajax.php') . '";
         </script>';
}

Just in case someone else is having the same issues.

I have another question if you don’t mind, is there a way to disable the request button if the author didn’t have a PayPal email address saved to their profile?

Thank you for the great work you’ve done with the plugin!