Jitters,
I was having that problem booking for October because the inventory of 33 seats was not posted as available.
I checked every day for about a week and then..... voila! It suddenly appeared and I booked the seat.
They only seem to have about one or two months of seat inventory online for some routes.
I got a bus from the airport to the office for $600 JA and one from the office to Negril for $1350 JA.
Peace and Guidance