You recently updated QuickBooks and now get a "Status Code 3340" message when working with invoices. Error states "This request cannot be processed from within a data event callback procedure".
In AvaTax for Quickbooks version 84 this is a known error.
To resolve, upgrade to version 85. Download the latest version of your integration under Home > Get Started > Download and Install your Integration Software. (Link for Production Admin Console)
If not available, please reach out to Technical Support.