Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/16c66f490e59f4403a6ce2ea18d39366.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563