Sorry, I realize I didn't post the clearest earlier. I was able to get fast passes for 3:55-4:55, 4:55-5:55, and 5:55-6:55. I originally had booked my party day fast passes and then when I tried to book my last non-party day of fast passes, I got an error message. I then deleted the fast passes on party day, booked the last non party day and went back to the party day. I tried for a 3:30-4:30 fast pass on party day and again got an error message. I then tried 4-5, 5-6, and 6-7. I was able to do the first two, but when I tried to add the 6-7, I got the error message again. I deleted those and tried for a 3:40-4:40 and got an error message. Finally, I tried for 3:55-4:55, 4:55-5:55, and 5:55-6:55 and that worked.
It could just be a temporary glitch right now, or it could be that they don't want you to reserve fast passes until closer to the 4:00 start time. I have no idea. They may still cancel my last fast pass, but if so, I'll try to move them around again. I would recommend though that anyone having issues play around with the times and see if you can get it to work like I did.