My agency called LH special accounts.
They told them it had to be sold in the existing PNR.
It was a round-trip originating in Europe and they said the system was looking at the inventory as if it was originating/being sold in Europe.
They said if the agency cancelled the existing PNR and resold the space in a new record it would look at inventory ex-USA and that would not be the same.
They said the agency would receive a debit memo for inventory manipulation.

The agency said well they have this with other airlines too.
They didn't really know if it was looking at POS (point-of-sale) or just being more difficult or trying to get more money out of an existing sale rather than a new one.
Kind of frustrating they play these games.