This is one of the most common managed Google Play issues reported by administrators.
The most likely cause is that your managed Google Play store is configured in Custom layout mode (also known as collections mode). When this mode is active, approved apps will not appear in the Play Store on managed devices until they are explicitly added to a collection.
Custom layout mode is typically enabled when an administrator edits collections within the managed Google Play iFrame in their EMM console. Once enabled, the store switches from showing all approved apps to showing only apps that have been placed in collections.
To resolve:
If you want all approved apps to be visible without collections:
Other possible causes: