Invite to App Does not receive Callback

Our dev team are trying to integrated  "Invite to App" feature functionality into our application, but they have noticed that they are no longer receiving callbacks, which was working fine in the previous version.

Destination was created, user age group confirmed (13+), build uploaded, and data use checkup are active. 

Cannot figure out what's wrong.

Could anyone please provide some insight into why this might be happening?