Please help: Why aren't all the instruments I selected to be in my score showing up?

I'm composing a piece with a lot of parts (standard orchestra). On the "create new score" thing, I clicked on all the instrument parts I wanted and they definitely showed up in the space on the right so I'm sure they're there. However, when I finished setting up the key signature and time signature, it only showed the first 15 instruments I'd selected on the actual score. I scrolled down and on to the other page but I couldn't find the other parts anywhere. Also when I clicked on Create- Instruments to add the instruments that hadn't shown up, I could see that I had added them and even if I added them again, they still didn't appear when I wanted to compose for them. Please help. I'm not sure how to solve this? Have I done something stupid?