Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a36ed1c3bc5c41777c7fa8ddc3bae4b7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563