Payment is fine. Paypal IPN History shows ‘Sent’ When payment is done and paypal back me to my success page, received firefox bug: When I click "continue", Paypal send request to ipn.php ipn.php doesn't create ipn_errors.log , maybe hosting doesnt allow ... But ipn.php doesn't work, because MySql doesn't update. It's posible $verified variable to be empty? I used for guide: https://github.com/Quixotix/PHP-PayPal-IPN
The error is exactly what it says. This happens in most cases because you are moving from an HTTPS url into a non HTTPS url. Is your website/IPN url using HTTPS connection?
You need to buy an SSL certificate and set it up on your hosting (search google on how to on your server/control panel). Once that is done, you will need to update your URL to use https instead of http.