When retrieving a list of orders, it's important to specify the status.
The documentation is a little unclear as the status param isn't listed in the body of the documentation, but it is shown on the endpoint 'callout'
/admin/api/2021-10/orders.json?status=any
If you expand the 'hidden' portion of the param documentation you can see the status column along with the potential values:
- open: Show only open orders.
- closed: Show only closed orders.
- cancelled: Show only canceled orders.
- any: Show orders of any status, including archived orders.