I ordered our MVMCP tickets last night. When I tried to make a PS at LTT they said they were completely booked for 12/5. Are there other restaurants open before the MVMCP officially starts?
You might try again at 90 days out. I've noticed a couple posts about MNSSHP (which I'm assuming is handled the same way, correct me if I'm wrong!) that people will go ahead and book LTT to make sure they have a PS for dinner, then when Crystal Palace opens up, they book that and cancel LTT.
I would call back just to be sure. Make sure you tell them you have tickets to the party and that they need to pull up the special events screen to book it. They can't book it the regular way.
I had this trouble the first day the MNSSHP tix went on sale. Of course there were tables I just needed to find someone who knew how to book it. Give it one more try before you give up!