Ultimate Guitar Pro is a cross-platform service.
To use your Android subscription on multiple platforms and devices you need to log in to an account your subscription is attached to.
Note: If you registered with Google, Facebook, or Apple, you need to use one of these options to log in.
Can't log in
If you were logged out of your account when you purchased a subscription in the Android app, it got attached to your device. In this case, only on this device, you can access Pro.
Here's how you can make your Pro subscription cross-platform:
Open the mobile app.
Tap on the Settings → Sign up.
Go to Settings again → Tap Restore purchases.