There are 4 separate versions of the iReal Pro: one for iOS, one for Android, one for Windows and one for Mac.
iOS
If you purchased iReal Pro in the iOS App Store, you can install the app on your iPhone & iPad & iPod (you can't install it on your Mac computer as it is a separate app)
Mac
If you purchased iReal Pro in the Mac App Store, you can install the app on your MacBook & iMac (you can't install it on your iPhone or iPad as it is a separate app)
Android - Play store
If you purchased iReal Pro in Google Play Store, you can install the app on your Android phone, tablets and Chromebooks (you can't install it on your Mac computer or iPhone/iPad as it is a separate app)
Android - Amazon
If you purchased iReal Pro in Amazon Appstore, you can install the app on your Fire tablet. You can't install the Amazon version on your Mac computer or iPhone/iPad.
Windows
If you purchased iReal Pro from the MS app store for your Windows PC, you can install the app into a total of 3 PCs. When you first purchased your Windows version, you would have received a license key, use this key to activate on your other PCs after downloading again from the MS app store.
Mac, iOS, Windows and Android are separate platforms with separate billing by Apple, Microsoft, Google and Amazon. Unfortunately we have no way to transfer licenses between different platforms.
When you purchase the app, the transaction is between you and Apple, Google or Amazon. There is no way to transfer licenses between them and even within Apple, there is no way to transfer purchases between the iOS App Store and the Mac App Store.
For Apple, we don’t have access to billing, we don’t have your name either and we receive limited amount of promo codes so we can't fulfill thousands of users' request who are transferring to new devices between different platforms.
Thank you for your understanding!