I don't know why it would be so, but it seems that the snapmanager exchange license is a prerequisite.
Have you tried installing the snapmanager exchange license ?
You can look up all of your own licenses using the Products > My Licenses tool on support.netapp.com.
Your post doesn't mention the version of DOT you're working with ?
OnTap 8.2 has simplified license model with one SnapManager license.
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff
Senior Consultant, K&H Research http://www.khresear.ch/
Senior Instructor, Unitek Education http://www.unitek.com/training/netapp/
(P.S. I appreciate points for helpful or correct answers.)