Ok so I just spent about 30 minutes on the phone. The CM had me call Online Help because he couldn't figure it out. I called Online Help and the man there was incredibly friendly. He looked into it and finally came back and said he wasn't sure why I couldn't book it. He said it fell into the gray area because the length of stay was less than the days on the tickets. At t hat point he said they had to look at the rules which were "length of stay OR max of 7 days (whichever is more)" and this one fell into the "max of 7 days" because of "whichever is more".
He then went in and booked my FP+ for me. Got Space Mountain, 7DMT (there was a lot of availability left), and BTMRR. He had to book them because there was no way to force the system to let me. Nor will I be able to modify them. He said if I want to modify them I have to call back in. Since I'm not after any of the hard ones like A&E I think we'll be ok. I opted to get 7DMT instead of Splash because I didn't want to be running back and forth across the park, plus, we'll be at
MNSSHP that night and can hit the other rides late in the evening.
Glad you all spoke up or I would have just waited 2 more days before trying to book and by then some FP+ may have been gone or it may not have opened up for me at all. We ended up with the following:
Rope drop to Buzz Light Year ride
9:30-10:30am - Space Mountain
10:20-11:20 - 7DMT
11:45-12:45pm - BTMRR
The only other "must do" rides we'll have will be HM, POTC, Splash and JC so I think we can do standby or hit those late in the night at MNSSHP.
On a side note, I had read here that once you use your 3 FP+ you can get a 4th via your phone. That is NOT the case. He said you HAVE to go to the kiosk to get the 4th and consecutive FP+. He said there is a lot of misinformation out there that people aren't aware of. Just thought I'd share that in case anyone else like me was planning on using their phone to get the 4th FP+.