I had FPs reserved for RnRC, ToT, and Star Tours to start the day.
When I arrived, I realized that I wasn't going to be in the park long enough to use my Star Tours FP, so I dropped it. RnRC was first on my schedule and ToT went down while I was in line for RnRC pretty much immediately after my FP time slot for ToT opened. I was awarded the "Anytime/most experience" FP when ToT went down. (So my advance ToT FP was converted to an anytime)
After RnRC, ToT was already back up and I used my anytime FP. I picked up another ToT FP while in line for ToT (it was for fifteen minutes from then - no brainer

) and used that immediately after my first ToT ride. Trying to get additional FPs was the issue from here.
I did use 3 FPs but one was the anytime. So, if I understand correctly, the anytime does not count toward the three and that's why I was having problems. I thought I could book another Tier 1 after using a Tier 1, but I couldn't. I guess I needed to use another FP in order to book additional Tier 1s or a FP for a ride I had already been on.