What is the issue, and how does it get resolved?

Refer to the exhibit.

User A tries to log in to the Cisco Jabber client, the login works fine, but the user cannot see their self-presence or other users’ presence in their contact list. The administrator checks the Cisco IM and Presence Server logs and sees an issue. What is the issue, and how does it get resolved?
A. The user credentials are incorrect; ask the user to change the credentials.
B. The user is duplicated in another Cisco IM and Presence cluster; unassign the user from the duplicate IM and Presence cluster.
C. Presence has stopped working for the user; unassign and reassign the end-user to Cisco IM and Presence.
D. The Cisco IM and Presence Server has CPU/memory issues; restart the IM and Presence Server.