Booking class is actually sub-divided by various rules which may alter availability. Common ones are point of sale (D may be available if ticketed in certain countries but not in others), and married segment logic (D may be available for O&D but not if there is a transit before/after the flight or vice versa).

LA532 operates EZE-SCL-JFK. Are you looking for EZE-JFK or SCL-JFK? Availability may be different.

I notice JL has a codeshare on the flight (JL7627). Availability on the codeshare may differ from the operating airline (could be better or worse availability).

Other routing options to consider are via EZE or GRU or GIG or MIA