Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/120b65f7c9c92ee3a63ce46a5c187931.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563