Shopify only allows certain specific values to be entered in the fulfillment_status field and any other values will be rejected by Shopify. To make things even more confusing, there are two fulfillment status fields! One on the order itself, and one on the 'Line Items' section. Which section you choose is entirely up to you as both are acceptable, the only time it makes a difference is if you import a live order that has some line items which have already been fulfilled and others that have not.
Allowable options to include in this field are:
- fulfilled
- unfulfilled
- pending
- restocked (this is only valid for the fulfillment status on the Order, not on the line item)
Any other values you provide for the fulfillment status will come back as an error by Shopify.