I tried to book the overnight Trenhotel from Hendaye to Lisbon at the Renfe website and, while all days before an on Dec 11th can be booked normally (expect Dec 5th, which is sold out) all other dates) show "Sorry, it is not possible to book at this moment". It does not show sold out as it does for Dec 5th. Is this train eliminated for good?
According to the Man in Seat 61 trains go on sale in Spain 60 days before departure. However here he says:
The opening of reservations can be delayed for dates after the twice-yearly timetable change in June and December, as they're always late loading the data. The 60/90 days isn't exact, indeed, I often find that Renfe loads trains as and when it feels like it, often less than 60 days and sometimes certain trains appear on the system before others. If you don't see the complete train service which you are expecting to see, and it's over a month to go before departure, the chances are that not all trains have been loaded yet.
So best to be patient. His Portugal pages confirm the information.