Have you installed the app itself? It should show in your Android Settings > Apps. If not, reboot, check you are signed in with the Google account you used to purchase the app, then download it from the Play store.

Some Play store install information
https://support.google.com/googlepla...14122894?hl=en

Reference to clearing the cache
https://support.google.com/googlepla...14121800?hl=en

Also make sure you have an internet connection after installing or if you are opening it for a few days in case the Play store needs to check.

You might find other information with a search for your specific error message.