Just trying to understand your scenario.
Looking at this error: Failed to connect to storage. Are you trying to add 'storage' from SnapCenter ?
So,
1) You have SnapCenter plug-in (for vmware or whatever) installed
2) You have a AD user or group created ? You log into SC and then add a user/group with SnapCenter defined roles ? Settings | Roles | Add..
Depending upon the 'Role', set of permissions are assigned (ex-create storage connection, resource group, clone, provision etc).
For example: In Active Directory, a group is created 'sc_managers', users are added to this group. Then, once you logged in to SC as 'admin', you go to settings, roles, and create a role/permission and assign a 'group' created in AD or chose from existing role that best defines what permissions you want to give. Then the users of that group with the defined 'role' will be able to carry out tasks that the role permits.
I don't know if I am following you?
https://docs.netapp.com/ocsc-41/index.jsp?topic=%2Fcom.netapp.doc.ocsc-ag%2Fhome.html