You need to meet the requirements for the MKG department users.

References:

https://docs.microsoft.com/en-us/microsoft-store/distribute-apps-from-your-private-store

Enable the users in the MKG department to use App1.

The private store is a feature in Microsoft Store for Business and Education that organizations receive during the signup process. When admins add apps to the private store, all employees in the organization can view and download the apps. Your private store is available as a tab in Microsoft Store app, and is usually named for your company or organization. Only apps with online licenses can be added to the private store.