Managed Play Store is empty on devices

Issues/behaviours we saw on playstore sometimes (each point independent):
- ensure no updates stuck in the playstore (circle top right > manage apps & device > updates)
- reboot the device once
- wiped playstore data so it needs to collect it again

But i found this (Source) :

In the Assignment tab, If you assign the app to a group under Required, app will be automatically installed on users phone, there is no action required from users end (Note: when using MAM solution, users still have to install the app from app store on iOS or google play store on Android manually). When the app is assigned to a group under Available for enrolled devices, the app will be available for installation via the Company Portal App for enrolled devices and user will have to install the app manually. Last option is to go with Available with or without enrollment.

Official definition of assignments:

Required: Select the groups for which you want to make this app required. Required apps are installed automatically on enrolled devices. Some platforms may have additional prompts for the end user to acknowledge before app installation begins.

Available for enrolled devices – Select the groups for which you want to make this app available. Available for enrolled devices apps are displayed in the Company Portal app and website for users to optionally install. Available assignments are only valid for User Groups, not device groups.

Available with or without enrollment – Select the groups for which you want to make this app available with or without enrollment. Apps with this assignment are displayed in the Company Portal app and website for users to optionally install without requiring the device to be enrolled. Available assignments are only valid for User Groups, not device groups.