Good but asked to pay again for same book – Piano Adventures® Player Review

I have paid $4.99 for level 1 and have been using to practice for a big while and now it asked me to pay again $4.99. I dont mind paying 4.99 for every book but to have to keep paying I think that is too much. And if it is a mistake who can help me to fix it.
Review by gateaux35 on Piano Adventures® Player.