Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0c50de28723cb9b815c2b9d5de23f568.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563