Sometimes Group Policy will not update correctly and the cause is a corrupt registry.pol file. This can cause numerous different problems such as Windows not auto-locking the screen after the correct timeout and some DNS issues.
Open up file explorer and go to:C:\Windows\System32\GroupPolicy\Machine
Rename the registry.pol file to something else such as _registry.pol
Windows Key + R and run gpedit.msc
You need to change any setting to trigger a new registry.pol being created
Example: "Computer Configuration / Administrative Templates / Control Panel / Personalization/ Prevent changing lock screen image" Change it and then revert it back to what it was before
Open up command prompt and run gpupdate /force