Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d1e0b98e72b43ba5b79a85c72d9d5c6c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563