Check the Facility settings.
In order for events to appear in a check-in facility, the Facility has to have Show Events enabled.
You may also want to check the Minutes to Show Events Before They Begin setting. The default value is 60 minutes, so if the event doesn't start for more than an hour, that is why it is not showing in the check-in yet.
Check the Facility Information for the event/time slot.
You may want to verify that the correct Facility has been assigned on the Event Details page. Events will only appear in Facilities that they are mapped to.
You may also want to check the facility information for the specific time slot that should be showing in the check-in. It is possible to have different Facility settings for a time slot than the overall Event Details page.
Check the event's Primary Time Zone.
If an event has multiple Locations mapped to it with different time zones, the event will ask you to set a specific Primary Time Zone.
If you didn't select a Primary Time Zone when the event was created, the first option alphabetically was chosen by default.
You may also want to verify that the Facility's time zone is correct. If the event's time zone and the facility's time zone are different, that may be what is preventing the event from showing when expected.