First of all, check your auditing settings:
In the Group Policy Management Editor, choose
Computer Configuration → Policies → Windows Settings → Security Settings → Local Policies → Audit Policy
Set the following audit policies:
Alternatively, you can set Advanced audit policies:
In the Group Policy Management Editor, expand
Computer Configuration → Policies → Windows Settings → Security Settings → Advanced Audit Policy Configuration → Audit Policies
Set the following audit policies:
Account Logon
Account Management
DS Access
Logon/Logoff