The session failed because Application Source Qualifier <Application Source Qualifier name> contains a vertical tree source definition with no PeopleSoft tree attributes assigned. (At least provide Tree Name and Effective Date.)
You did not import PeopleSoft tree attributes into the created tree source definition.
Import tree attributes in the created tree source definition. You can import the tree attributes in either the source definition in the Mapping Designer or in the session properties. You must enter at least the PeopleSoft tree name and its effective date.