Explanation:
How To Troubleshoot ISE Failed Authentications & Authorizations
Check the ISE Live Logs
Login to the primary ISE Policy Administration Node (PAN).
Go to Operations > RADIUS > Live Logs
(Optional) If the event is not present in the RADIUS Live Logs, go to Operations > Reports > Reports > Endpoints and Users > RADIUS Authentications Check for Any Failed Authentication Attempts in the Log

Reference: https://community.cisco.com/t5/security-documents/how-to-troubleshoot-ise-failed- authenticationsamp/ta-p/3630960