When you try to login to Windows, you might encounter this error.
“The Group Policy Client service failed the logon. Access is denied.”
When you click OK, the system will return to the login screen. This is a registry permissions issue; you can delete the corrupted user profile or follow the below steps to gain access. I recommend backing up the registry before you begin, particularly if you are unfamiliar with registry editing.
4 Steps total
Step 1: Login as admin
First login to Windows with a working administrator account.
Step 2: Load user’s profile hive in regedit
Open the registry editor and select HKEY_USERS in the left pane.
Click the File menu and choose Load Hive. Verify that the “Files of type” box says All Files.
Navigate to the profile folder of the user who cannot login (for example, C:\Users\) and select NTUSER.DAT, then click Open.
Enter a temporary name to use for identification (for example, BROKEN_USER).
You will now see the name you gave it under the HKEY_USERS key.
Note: if you don’t see NTUSER.DAT, you need to display hidden files or type ntuser.dat in the file name box.
Step 3: Fix permissions
Right-click on BROKEN_USER and click Permissions.
Here you should see at least three entries: SYSTEM, Administrators, and the name of the user who can’t login. If any of these are missing, you need to add it and give Full Control permissions.
Step 4: Finish and restart
Once you have all three and they have Full Control permissions, click BROKEN_USER (if it’s not highlighted), then click the File menu and select Unload Hive.
Close the registry editor and restart the computer. You should now be able to login successfully with the affected user account