Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d00b9afbfd4a19b6a9e8e2b5831a7d21.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563