Had the same issue today.
Turns out I had not added the storage controllers to the setup section of VSphere. (Although I had added them to the NetApp tab)
To add the hosts open the VSphere client, click the home button, then the NetApp button under Solutions and Applications.
Click the backup and recovery tab from the left and click setup.
Add your storage systems to the list and the backups should now work.
Cheers
Steve