Moved provisionally to Encryption: ePO Managed for better support.
if you are using EEPC and you are enabling Preboot and SSO the user has to enter the password at the windows logon prompt. This is made by desing.
1) enter password in Preboot
2) enter password at Windows logon prompt
EEPC compares the password from the Preboot Authentication Prompt and the user credentials provided by the Windows credential provider.
Afterwards the password in the Preboot Partition and the password for Windows Logon are in sync. If the user then changes the password, this change is also written to the Preboot Partition.
Have you activated the Preboot Authentication?
The 802.1x credential provider is not in the standard format and contains additional fields and is not compatible with the Drive Encryption credential provider. KB71891