Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/cff4090127b6cebbddacb31b5b15b21e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563