Replies from DLP can take a while.
Did you already purchase your tickets or booked your hotel (package)? When I look at the Dutch website, it only lets me book if I have or book the paid FP all at once.
It also says it's possible to call if your date is sold out.
I would suggest to buy them in advance if you can, as they can sell out.
When selecting the different types (each FP ride only once or all day), keep in mind that there are only 8 FP rides over the 2 parks and Peter Pan is almost identical to the ride in the US, and Buzzlight Year is closed for renovation and replaced by the Flying Carpets over Agrabah (Dumbo type ride in the Studios).