Hi Robert,
I, myself, have just tried to make an Advance Dining Reservation on the Walt Disney World website for the Fantasmic! Dinner Package for the week commencing March 5, 2017 and although it shows that dates are available to book up to and including March 10, 2017, you are quite right that no tables appear to be available, no matter what date or restaurant is selected.
It sounds to me as though there may have been a slight delay in loading the tables for the
Fantasmic! Dinner Package onto the online dining reservation system.
I would simply recommend that you keep checking for availability on the Walt Disney World website over the next few days to see if the tables have been loaded or, you could call and speak to a Cast Member on (407) 939-1947 who maybe able to shed some light on the situation.
Wishing you a magical trip filled with memories which will last a lifetime!
Emma