A user cannot authenticate to SSL VPN. You have verified the user is assigned a user group and reproduced the problem, confirming a failed-login session. You do not see an indication of this attempt…

A user cannot authenticate to SSL VPN. You have verified the user is assigned a user group and reproduced the problem, confirming a failed-login session. You do not see an indication of this attempt in the traffic log. The user is not using a client certificate for login. To debug this error, where in the authentication process could the solution be found?