If you are using the waivers in your org for the volunteer Check-In, please make sure that you enable only the Signup button in the Add New Volunteer screen and on the search volunteer screen for the Job/Shift.
We suggest you enable only the Signup button on the Add new volunteer screen and on the search volunteer screen, is because the volunteer should first signup for a Job/Shift. Then sign the waiver and Check-In.
If both the Signup and +Check-In buttons are enabled, the volunteer might only hit the Signup button and see the details as Checked-In to the Job/Shift on the Kiosk app. But the volunteer is not actually Checked-In.
To fix this issue, we suggest you enable only the Signup button in the Add new volunteer and on the search volunteer screens by following the instructions here.