I paid for an app from the Google Play Store some years ago. I have been using it successfully up to yesterday.
Today, I tried to use it and it complained I wasn't licensed and redirected me to the Play Store app. However, that just gives an error "Something went wrong", or "Try again". The Play Store app still lists the app as being installed. All my other paid-for apps appear unaffected.
After some testing, I worked out that the app seems to have been deleted from the Store. I have emailed the author and am waiting for a response.
If I don't get a response, are there options to recover the use of the app?