I installed the app on another device, but I don't see Heather, or the free voice I picked.

On your new device:

1. In iOS Settings, check that you’re logged into the Apple ID you used to purchase the app.
2. In iOS Settings, check that you’ve enabled iCloud, using the same ID as your other device.
3. In iOS Settings, check that you’ve enabled iCloud Drive.
4. If you passed all 3 steps above, please turn off iCloud Drive and turn it back on.
5. Terminate the app and restart. Now your free voice should be available.