Great Movie Ride isn't available for the week I am there either (9/20-9/26).
It might have something to do with the tiering system. Not everyone can or will go on Tower of Terror from tier 2, but everyone will go on Great movie ride. And since those are the only really good attractions that need fastpass at DHS when its slow, then it might already be gone.
The problem is that they force you to take 3 fastpasses. So you got Toy Story Mania or RRC... so what else are you going to burn your 2 others on?
I actually got a 9am muppets fastpass. I doubt I will use it. This way I can have them run out and grab fantasmic as my 4th (or reschedule that muppets FP to fantasmic once fantasmic is released). Once Fantasmic rreleases, you might have some availability.
Or... its under rehab.