Hi,
Thank you for your kind words 🙂
Well, the issue is then, that the plugin for some reason tries to query the secure version of the handler URL, staring with “https://”, while the site is running “http://”, that perfectly explains the issue.
That URL is requested from WordPress, so I suspect that somewhere on the site back-end, the site URL is not configured correclty. It should be http://partaxpress.com/wp-admin/admin-ajax.php
If that is correct, then this might be changed via a custom code somewhere. It needs to be corrected for sure, because that ajax handler URL is used by the WordPress core as well.