Typically when you see a time out, it is from the client not finishing the auth request. I could be multiple issues. Most common is issues with the NAD device (switch/Wireless).
You could have latency issues/route issues, ect. Depending on the device you should be able to look at the clients logs and see where it is giving up.
I have also seen this issue when its mobile devices. Maily phones. The user will grab the phone and look at the time but will put it away before the client finishes the auth.
You can also enable debug on CPPM to get a more detail view and export the logs to see the full auth request, but again if there was an error with cppm then you would see a fail or vailed auth. Not a timeout.