Manual Multilevel Controlling in PPM5

Hi Experts,

When defining the multilevel controlling assignment in the Project Management area, we are able to select a PS project and see it in the screen, but the Assign button in it is deactivated so we cannot assign any WBS element to the structure.

What are the criteria to enable the assignment between PS and PPM?

Note: the WBS element has the Planning and Accounting assignment checks enabled.

Best regards,

Neil