As others have noted...if you are staying at a Disney hotel...wait to buy your tickets from your resort concierge.
Last year was our first trip to SHDR and thought that was really weird. We kept trying to buy tickets online and we were not able to do so (was rejecting our credit card). Even after speaking to our CC company it was SHDR that was rejecting the card, not our card company. We even tried using our travel card that was loaded with local currency...still would not allow us to buy tickets online. After many phone calls to SHDR they noted this happens a lot with their online system and said we can just buy tickets from the hotel.
You are guaranteed park tickets as a resort guest with a valid reservation.
Flash forward to our check in at the Shanghai
Disneyland Hotel.
Was no issue buying the tickets and getting our hotel fastpasses. Just know ahead of time what attraction and rough time you want your hotel fastpasses for, you have the let them know right then and there. The hotel's concierge arranges the fastpasses for you and they will load into your SHDR account.
You can not select your hotel FP from the app.
There was other foreign couple that was having issues with their tickets they bought online and trying to get the hotel fastpasses
While the Disneyland resort is amazing...their English is pretty good...but they were not able to clearly understand or communicate the issue to this other couple. This couple was clearly upset and really confused on what was happening. Same the the hotel staff...as more and more cast member cam out and were trying to explain the issue.
From what we understand the hotel was not able to refund their online ticket purchase. Hotel concierge has to sell you the tickets on site to get the extra Fastpasses.
I think this is due to the fact that SHDR has a real issues with fake tickets and fastpasses being sold.
They take your photo with the ticket to use as proof that the tickets are "official" Disney tickets