If your Application event log contains:

Event ID: 1000
Event Source: Userenv
Description: Windows cannot read the history of GPOs from the registry

you have some missing or corrupt registry entries. This causes Group Policy to NOT be applied on your computer.

To fix this problem:

1. Use Regedt32.exe to navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Group Policy\History.

2. On the Security / Permissions menu, make sure that the History key and sub-keys have the following permissions:

Administrators Read, Full Control
Authenticated Users     Read
System Read, Full Control

3. Delete all the sub-keys of the History key. DO NOT delete the History key.

4. Run secedit /refreshpolicy machine_policy /enforce.

5. Check the Application event log for Event ID 1704.

NOTE: the History sub-keys are re-created.