Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7d4d5b9e4d5fe8e643a17d781bce674a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563