Thanks for providing the exact error you've received when sending customer data to QuickBooks Desktop (QBDT) through a web-connector.
I've checked through this article: Fix common Web Connector errors and couldn't find QBWC1042. I recommend contacting our Intuit Developer Team. It's a place where different developers and coders help each other with integrations and programming. They can check and isolate what's causing the unexpected error so you send customer data to QBDT.