Checking that Group Policies are being applied

If you notice that Group Policies are not taking effect, try the following.

1. Win+X > Command Prompt (as Admin).
2. gpupdate /force
3. gpresult /r
4. In the command output, look for the section Computer Settings > Applied Group Policy Objects. Check that all the linked GPOs appear here.
5. Start Menu > "Local Security Policy", and check through tree. Some items will be greyed out, indicating that Group Policy is overriding these settings. There should be no error "The Group Policy security settings that apply to this machine could not be determined". If there are greyed out items, and there is no error appearing, then Group Policies are being applied correctly. There is no need to follow the remaining steps.
6. The error "The Group Policy security settings that apply to this machine could not be determined" is caused by database corruption. To fix it, follow these steps:

a. Win+X > Command Prompt (as Admin)

b. "esentutl /d %windir%\security\database\secedit.sdb"

c. "esentutl /r %windir%\security\database\secedit.sdb"

d. "esentutl /p %windir%\security\database\secedit.sdb"

e. "gpupdate /force" (gpupdate should take longer to run following the repair)

f. Start Menu > "Local Security Policy", and check through tree. Some items will be greyed out, indicating that Group Policy is overriding these settings. There should be no error "The Group Policy security settings that apply to this machine could not be determined"

Another trick: try running the Group Policy Object Modelling Wizard (it's in gpmc.msc) to find which policies are the winning RSOP for each setting.