Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f1e46f75f434f14363252578a16d9c7b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563