You can open your progress in Simply Piano on multiple devices by logging in with the same email address you used previously. This includes across Android and iOS devices.
We recommend you first double check which email you used on your previous device. Go to Menu > Settings > My Account in Simply Piano on the the previous device to see the email address used.
If you see Anonymous on the My Account page, this means the account was not linked to an email address and you will not be able to open your progress on another device. Just press the pencil (iOS) or click Change Email (Android) to change this to register with an email and you will be able to use your account on another device.
Have more questions? You can talk to us through the app. Tap on Menu > Settings > Send Us Feedback / Contact Support :)