Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b004e93e6f7abaea64c62a69ee1a5ddb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563