Can not create a case from Threat Analysis Section or from detections section

Hello,

I am trying to create a case from the threat analysis center.  But when I go to the "Cases" section, the "Create a Case" button is missing.  Also, when I go to the "Detection Section", I choose a threat, and then click on create a case, but under Assignee it says No Results Found.  So, I cannot choose an Assignee.

Anyone know how to fix these issues?