Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7833b1bf33e9e4747d56c50b4c228e7c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563