Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/54668bd0c5fa0ba17f69482d1ad7e6f1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563