Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/de4e9d78b2b72b6fc61a60d30f490b0c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563