Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7e17d6a760b7c794fb19a6a7b9d4e238.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563