@Mohamed Umer, Thanks for posting in Q&A.
From your description, we understand that you configured a policy that automatically locks the screen if there is no activity on the device for 1 minute and it worked, but when you change the time to 15 minutes, it does not worked.
For the issue, I have done the test in my lab and I found that when the deployment status of this profile is succeeded, restart the device that assigned, I wait 15 minutes and the screen locked.
Therefore, please check policy deployment status, if succeeded, restart your assigned device and wait your set times to see if succeeded. However, if your policy is applied successfully and device still does not lock screen, please go to the registry which locate in Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\current\device\DeviceLock MaxInactivityTImeDeviceLock to see if the policy value matches the value on Intune, if not, please restart your device.
If above information is fine, but the device cannot lock the screen automatically without activity after 15 minutes. Please gather the following information so that we can better help you.
- Please export the settings for Group Policy to see if you have the same policy in Group Policy as in Intune, because Group Policy is applied with precedence over Intune policies.
- Run cmd as an administrator
- Run gpresult /h c:\test\result.html
- Please take a screenshot of your setup in Intune.
Hope above information can be helpful. 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.