Symptoms
An Administrator may not be able to correctly Enable Agents through the Live Assist Administration Portal. Agents or Supervisors marked as enabled in the Admin Portal, may not have the expected role set; preventing them from seeing the Live Assist Agent Widget when they log into Dynamics 365. In this case, the Agent's role has not been taken or correctly set.
It is also possible that the Administrator may not be able to perform any action within the Administration Portal.
Solution
In some Dynamics 365 instances, it is necessary for specific privileges are allocated to an administrator.
Within Dynamics 365, review the User Settings Entity within the Business Management tab. Verify the Live Assist Administrator role has the READ privilege enabled.
This will allow the Administrator to access the Live Assist Administration Portal and let them reassign the Agent role to any users affected. If an Agent was enabled but could not load the Live Assist Agent Widget, it will be necessary for the administrator to disable then enable that user for the change to take affect.