Chord ai does not store any account information. You may notice that there is no login screen in Chord ai. Your user data is retrieved and sync across iOS / iPadOS / MacOS devices through your Apple account and iCloud. Same goes for your purchase information, which you can consult in your account settings https://support.apple.com/HT204088

Chord ai is also available on Android but the two apps do not share any information, which means that there is no user data sync between iOS/iPadOS/MacOS and Android. If you wish to subscribe to Chord ai Pro on both OS, you will have to subscribe on both iOS/MacOS/iPadOS and Android.