that's actually a good question... it's a glitch with the store (the game doesn't know about payments, so basically it does whatever the store apple/google tells it). it's been going on for ages and neither me nor the store has figured it out yet. I must say it has improved a lot, 2 years ago it happened to almost everybody, nowadays it's only to a few accounts. So it seems related to some credit cards or countries, who knows.
In any case, I've been working with them for ages trying to get a fix for everyone.
btw, is it solved? it shows as subscribed here