This happens when there’s no application in Web Connector and you selected Select None.

What you can do?

If you haven’t yet, connect your application:

1. Prepare your application's .QWC file. You need this for installation. If you don't have this, you can get it from your application provider.

2. Add your application in Web Connector.

Note: If you still get this error, reach out to Intuit Support.

Reference: https://quickbooks.intuit.com/learn-support/en-us/set-up-payments/fix-common-web-connector-errors/00/203305