The app installation status may display as "Pending - All licenses are in use or the license is not assigned yet" due to a volume purchasing internal error 9603. This error typically means that the volume purchasing services handling the license assignments could not provide timely processing and nothing is wrong with the request itself.
If app license assignments continue to not process over the course of a day, diagnose and alleviate this condition as the root cause by performing the following:
Confirming error 9603 at server level
Re-syncing licenses for impacted devices
Note:
Depending on the app and installation environment, this scenario could also result in a failed status and display the message "No license was found for app". This message may display due to unavailable licenses.