The Invalid Join error is issued in the following situations:
Cannot use the <entity> entity twice in the same join condition. Change the join condition to use another entity: the same entity cannot be use in a join condition.
Edit the join condition to use two different entities.
<Structure> cannot be used in a join condition since it is a Structure: cannot use a structure in a join condition.
Remove the structure from your join condition.
Clicking the symbol will direct you to the source of the error.
About Error Messages