A few years ago, The Pokemon Company launched Pokemon Duel (Free) which is a Pokemon board game on the App Store and slowly brought it to more countries. It arrived in USA in January 2017 which is a while after Japan. Today, the description of the App has been updated to announce the termination of service for the game this October which is less than three years after the game debuted in USA. As with most games like this that end service, you will not be able to play a majority of what the game offers if not all of it when October 31st arrives.
We have a thread in our forums for it but it is likely not many people will still bother with it considering there are less than six months before service ends. Have you spent money in game through the Player Pass? It is pretty disappointing seeing big brand games like this go away but this is a harsh reminder that almost any online only experience you enjoy will not be playable in the future when service ends.