Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d15e439a79b94a8be1eb8a85c8461775.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563