Did you purchase the app on the Google Play Store for Android, but it didn’t download?
That’s an issue with the Google Play store, since that’s where payments happen and downloads come from. We don’t have any involvement in the process of purchasing or downloading the app, that is facilitated by Google.
Usually it’s an issue with needing to clear the cache for the Google Play store app, but they have some other recommended steps if that doesn’t work. You might need to contact Google Play support to straighten it out, but here is a support article about that. It’s a pretty common issue they haven’t fixed yet.