Windows 10 Creators Update build 1703 came with a new set of .admx and .adml policy definitions. Everything was working fine but Microsoft changed the name of the Windows Store policy definition files and borked up a bunch of random unrelated GPO. If you view affected GPO in Group Policy Manager on your domain controller you may see this error in place of your normal settings information.
The error is:
Namespace ‘Microsoft.Policies.WindowsStore’ is already defined as the target namespace for another file in the store. File \FQDN-DC\SysVol\domain.com\ Policies\PolicyDefinitions\WinStoreUI.admx, line 4, column 80
To fix this issue go to your sysvol. Usually at path above or something similar:
Delete the file: WinStoreUI.admx
Rename file WindowsStore.admx to WinStoreUI.admx
\\SysVol\ yourdomain.com\Policies\PolicyDefinitions\en-US (or whatever your language is)
Delete the file: WinStoreUI.adml
Rename file WindowsStore.adml to WinStoreUI.adml
Refresh the settings view in Group Policy Manager and you will see that your policy definitions are working again.
You are done!