Hi Jeffrey,
Are you using Anyconnect NAM as supplicant? If so, you can use NAM profile editor to change the settings. BY default the outer tunnel in dot1x uses anonymous. Also not sure if you are using username/password or doing a single sign on.
In any case, please look at the ISE logs and NAM logs(under windows logging) to determine the cause.
It depends the type of authentication you use etc in NAM. If the problem persists even after debugging and is impacting users please open a TAC case.
Thanks
Krishnan