Setting up auditing on HR_ASSIGNMENT_SET_AMENDMENTS

I am attempting to enable auditing on the HR_ASSIGNMENT_SET_AMENDMENTS. I select the columns ASSIGNMENT_SET_ID, ASSIGNMENT_ID (key values) and INCLUDE_OR_EXCLUDE, and save successfully.

I then run the concurrent process AuditTrail Update Tables, but it seems to wipe out the columns from the column-list for that table. I am expecting to see a table HR_ASSIGNMENT_SET_AMENDMENTS_A, but there is nothing.

Any ideas why that would be? We already have auditing enabled on other HR tables/columns, so the schema is already enabled for auditing.