There are a few reasons why a date might be showing unavailable.
If you are trying to book a date that is a few months away, please note that the booking window is 10 weeks in advance. Dates further out than 10 weeks will open up as we get closer so check back then!
It may also be either sold out or the hotel has blocked out that day for day guests because the hotel is at capacity. There is a small chance it could open but it is best to book another available option or hotel.