How to associate a Receipt to a PO using the sage web api?

I am trying to create a receipt and associate it to a Purchase Order using the web api.
In the payload of the Receipt I have added the Purchase Order Number and it's sequence key. So in the receipt lines. On the sage side I see the receipt being created. However the receipt is not associated to a Purchase Order Number. Nor any of the details.

I want to do one receipt to one purchase order. Not multiple, figured out this should work. But I have no success on this. Please advice. Using receipts not being associated to a Purchase order is an useless "feature" for our use cases.