Thanks for visiting in this forum, @billing101. I'm here to direct you to the appropriate support team that can help you address and resolve the error message you've encountered.
It appears that you've already verified that both the WooCommerce customer and the unified customer in QuickBooks have valid email addresses associated with them. However, considering the specific error you're encountering, it's advisable to thoroughly review the integration settings between these software.
With that said, I encourage you to contact QuickBooks Connector's customer care team, as they have the specialized tools and expertise that can help you identify and resolve the cause of this matter.
In addition, if you want to learn more and get a quick overview of your business and financial records in QuickBooks, here's an article you can check: Add and manage customers.
It's our utmost duty to ensure that your concerns are fixed promptly, @billing101. We will always have your back if you need further help in regards with this matter.
