@Aran Billen,Thanks for posting in Q&A.
From your description, I know you want to enable device lock when screen lid is shut but failed. To clarify this issue, please check the information below.
1.Check whether the device edition is support and scope is device.
- Pro
- Enterprise
- Education
- Windows SE
- IoT Enterprise / IoT Enterprise LTSC
2.Check whether the targeted device applied the policy. Registry Location: Computer\HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Power\PowerSettings
3.Check if there are related errors in Event Viewer. Location: Event Viewer > Applications and Services Logs > Microsoft > Windows > DeviceManagement-Enterprise-Diagnostic-Provider > Admin
Please try above information, if there is any update, feel free to contact me.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.