Has anyone had their scheduled fast pass cancelled and something else scheduled in its place? On November 21st I had fast passes scheduled for my sister and niece for Meet Elsa and Anna, while my mother and I had fast passes scheduled for the Haunted Mansion. It was all fine last week, but looking today now the Meet Elsa and Anna is gone and replaced with Haunted Mansion (which we aren’t even sure my niece will go on). Of course now three is no available slots for Elsa and Anna. What’s going on??
Is there a Christmas party that day and is you FPP time close to the party time? Happened to me with the Halloween Party a couple months ago. I was able to get what I wanted to fit in eventually.
Nope, no party that day
did someone else in your party change them? If they are linked to you, they may have thought to change it so you are all together.
Nope, I am the fast pass manager. This had been discussed by the group ahead of time. My mother doesn’t know how to change them (or find them) and my niece really wanted to meet them 
This was something she was really looking forward to so it’s very frustrating after I managed to get it.
Call WDW IT at 407-939-7765 or 407-939-4357 - they should be able to help you get to the bottom of things.
Definitely call. In the last few months I’ve read about this happening to many people and some said Disney reissued the fastpasses when they called because it was a glitch in the system. Hope that is the case for you. Good Luck!