As you may know, many Japanese hotels do not load anything other than rack rates, and sometimes not even those, until 3 or 4 months in advance. If you are searching earlier than that, it might explain your problem.

It may or may not suit your needs, but I found the Comfort Hotel - Hakata-ekimae to be very convenient if a bit western for some tastes. It is a very large, many-storied hotel that is only a short walk from the station and several ramen places. Large beds for Japan, fast internet and bookable on the American Choice Hotels site. Search on Fukuoka, not Hakata. Just FYI in case your preferred choice is unavailable.