If you have an upcoming (or already had a) MyMagic+ (MagicBands & FastPass+) eligible reservation, you should be able to book FP+ if you link your voucher number to your MDE profile.
You would still need to visit a park ticket window or guest relations location at WDW to exchange for your actual pass.
I have a resort stay too, but yes I was able to. The scan app for MDE, on smart phones only worked on my ticket and my youngest dd. I had to call and the phone operator was able to help me link them.
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