Hi there, online and ready to get started ASAP. I have many years experience working with Magento and various e-commerce software. I will get started immediately because this is a critical error if it's preventing users checking out of your site. Are you able to reproduce the error on your end too? Or does it seem to be working for some users and not others? What is the store URL so I can test on my end?
Let me know.
Thanks,
James