Update all client Agents to be current, then in NAC Manager:
- Select All NAC Appliances (the applicable appliance group)
- Select the NAC Appliances tab
- Right click on each Appliance
- Select Manage Appliance Certificates
- Go to the Agent-based Assessment section and click the button that says “Use Internal Certificate”. (When you do this the status will change from “uses the legacy cert” to “uses the internal communications cert”).
- Click close and perform an Enforce to the appliances.