Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2e4afd2609ab57d1f63a01be585d9c90.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563