What can cause this issue?

An administrator receives an “HTTP 401 – not authorized” error for the Email Notification Service (ENS).

What can cause this issue?
A . A wrong username is set on the ENS server.
B . The Cloud Notification Service (CNS) is unable to authorize EN
D . The Apple Push Notification Service (APNS) certificate is not valid.
E . An ENS Service Account is not a member of the local admin group.

Answer: B

Explanation:

Reference: https://kb.vmware.com/s/article/50122031