Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e3d8c5dffd6a4a7ebf81af463de18b0c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563