Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c9a11c125a4f6ee25cf6d4f783d33daf.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563