The way a NDC booking can be issued is determined by the pricing option you choose when creating the PNR. If you get a ticketing error, it is likely because you are trying to issue on a different Form of Payment (FOP) than what you selected when making the booking.
Cash: Has to be sent through via a booking form for the Admin team to issue on the AT's cash account - cannot be issued on your credit card.
Credit: Has to be issued on your credit card - cannot be issued at nett on the AT's account
You cannot change the form of payment once the PNR has been created, you have to issue with the chose FOP or rebook a new PNR