Network Users

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