415 Usupported media type on get for orders

Using this end point: 'https://XXXXXXX.myshopify.com/admin/orders.json?fulfillment_status=unshipped’ on get call (which by the way works for several other stores I do fulfillment for) the api returns the error in the subject. Even though a get has no payload I do supply the header to include ‘Accept: application/json’. Any insight here would be helpful.