Windmills Shuttle not able to book

Hello, I just bought an AmsterdamPass card in and I want to take a Shuttle to the Windmills at Zaanse Schans witht the following option https:/…20Shuttle

There it says that I should book in advance and the link takes me to this other website. there is a button with the "BOOK NOW" option but once it pops up there's no option to actually Book. I checked that website and other tours have the real "Book" button, but not this shuttle.

Has anyone face this same problem? Do you think I can make it directly to the Shuttles Company with my card in the day that I'm supposed to travel? I can do that but I'd prefer if I can book in advance to plan the rest of the attractions i want to visit.

Thanks in advanced.