If there are no available licenses to use to distribute the app to users, computers, or mobile devices, you can purchase additional licenses for the app that has the pending app installation. You can determine if you need to purchase additional licenses by:
Viewing pending app used licenses
Performing simple or advanced volume content search for pending apps
You can view the used licenses for the volume purchasing location that was used to purchase the pending app. This allows you to determine if all the app licenses are in use.