Hi,
The " Clean Access Server could not establish a secure connection to clean access Manager" error message is seen when the CAS is not able to communicate to the CAM via a secure connection. As specified in the error message, you need to check whether the CAS and the CAM are able to trust each other or not (i.e., the certs of the CAS and the CAM should be under the trusted CA of each other) and if the certificates are valid or not. Please check the status of the CAS on the CAM. It should be showing as "Connected". If the status is not connected, please ping from the CAS to the CAM or vice versa to check whether they are able to communicate.
Let me know if it helps.
- Srilatha