Issue with magento 2.1.8

I have purchased Ves theme for magento2 from your site.
I am facing issue while executing compile command.
[RuntimeException]
Class Magento\Framework\Serialize\Serializer\Serialize does not exist!
Please refer same in attached file.
Can you please check on priority and let me the know the solution?

ThemeError|690x133

The best way to get the support is Contact your purchased Theme Author. Contact Author because Item Author are best expert about their Item functionality. Don’t worry just contact Author. Author will be very happy to assist you.

Thank you for your suggestion.