Have you changed the event from "Tentative" to "Confirmed" in marketing calendar?
The event will show up in the app within seven days of the event date, provided you have scheduled the event. Are you able to confirm whether you've set the event date and time in the program using the scheduler?
You will also need ensure that the relevant steps for check-in success have been set in the program channel/tags. For example, the status 'Registered' should have the mobile check-in status marked as Registered.