Bookings with payment status “Paid (voucher)” have the type “voucher” via API. By default, in operator/bookings response are just bookings included with type "booking".
This information you also find in our API documentation: https://sandbox-api.regiondo.com/docs/#!/Supplier/supplier_bookings
If you need to include all possible types of bookings including "voucher" into response, you need to send the parameter type like "offline_reservation, booking, voucher".