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 many hotels only open up dates a few weeks out. Dates further out may open up as we get closer so check back then.
It may also be 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.
If all days are showing unavailable, that hotel may not be offering day passes at this time.