Call Queue Not Ringing on User's Android Smartphone?

This is specifically about Microsoft Teams

User is part of a group, group is assigned to call queue as agents

User is having an issue where incoming calls from the Call Queue are not ringing on the Teams Mobile app on their cell phone (unless the app is actively open on their cell phone and the phone is unlocked/awake).

When the Teams Mobile app is in the background or their phone locks/sleeps the incoming call does not ring on their cell phone.

If a call is transferred from another user in the org. to their direct line, it rings with no problem on their cell phone, even if their phone is locked/asleep.

Why does the Teams Mobile app notify them about calls to their direct line but not about calls from the call queue they are assigned to (calls come in fine on Teams desktop client)?