Cash discount may only be granted up to 0.000 % Message no. F5233

I have researched sap.com and the forums, and no one seems to have answered this question.

Shall I post it to the Financials Board maybe?

I was doing a Miro transaction against a PO with some outstanding unpaid Goods Receipts documents.

I got this error:

Cash discount may only be granted up to 0.000 % Message no. F5233

I checked the cash discount percentages configured per company code, and it's blank... what is wrong here?