A chapter or some stones are missing

Almost always this is the app showing you something it remembered rather than something it asked for.

Try, in this order:

1. Pull down to refresh the book or your library.
2. Close the app fully and open it again.
3. Check you are signed in to the right account — stones and unlocks belong to an account, not to a phone.
4. Check for an app update.

If you paid and the stones have not appeared, give it a minute: a payment and its stones are two separate things arriving, and the second is usually seconds behind. If they are still missing an hour later, tell us and quote the reference from your receipt. You have not been charged twice and nothing is lost.