The error is reported if you have selected a test object in the test structure in
Test Designer and click Open source model in the Start tab bar.
Error message
The model associated with the test node is already open.
Cause
The source model is already open. This happens if you have previously opened the source model for a different test object that has an occurrence in the same model.
Solution
Click OK in the dialog and then click in the tab for the open model.