Hi there,
The first place to check is the Scope Tab on the Group Policy Object (GPO). If you are configuring a computer side setting, make sure the GPO is linked to the Organization Unit (OU) that contains the computer. If the GPO configures a user side setting, it needs to be linked to the OU containing the correct user.
Next check the Security Filtering settings in your policy. By default, all new GPO objects in the domain have the permissions for the Authenticated Users group enabled. This group includes all users and computers in the domain. It means the policy will be applied to all users and computers within its scope.
Here is a link that has some additional troubleshooting steps which you can try and see if helps in overcoming your issue.
10 Common Problems Causing Group Policy To Not Apply https://social.technet.microsoft.com/wiki/contents/articles/22457.10-common-problems-causing-group-policy-to-not-apply.aspx
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