Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/81a7abb5a4ec165fe3b9cf9ac5d6d749.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563