Click on your App Store, as detailed below, for instructions on how to see your purchase history:
- See your iTunes purchase history
- See your Google Play purchase history
- See your Amazon Appstore purchase history
The first possible reason is that you purchased the in-app upgrade to the free version in the past, and this time you purchased the Pro version (or vice versa). Each of our topics comes in two versions: an upgradeable free version and a pay-up-front Pro version (with a yellow "Pro" banner on the icon). The upgraded free version and the Pro version are equivalent, but not interchangeable.
The second possible reason is that you may have inadvertently created an additional iTunes account in the past, and you were signed in to one account at the time of the first purchase and you were signed in to a different account at the time of the second purchase.
If you inadvertently purchased both versions, please contact support so we can help you with a refund of the extra purchase.