The Pokémon Company has announced that Pokémon Duel will cease operations on October 31st, 2019 after 2 and a half years. The Game launched on January 24th, 2017.

Pokémon Duel - End of Service - October 31st, 2019

Thank you for playing Pokémon Duel!

Since starting services for the game on 1/24/2017, we have received a lot of support from our players. However, we regret to announce an end to game services starting 10/31/2019 at 01:59 (UTC).

Date of End of Service: 10/31/2019 at 01:59 (UTC)
Once game services are ended, you will no longer be able to install or update the game or transfer your account. Additionally, if you already have the game installed, you will not be able to continue using the app, barring certain functions.

Regarding the termination of item sales: As of 7/27/2019 at 01:59 (UTC), we have ended the sales of paid items, such as gems.

Regarding Player Pass: For any player who has purchased the Player Pass, the Player Pass will not be renewed after 7/26/2019 at 01:59 (UTC). Players will not have to make any changes to their accounts.

Notes:

• Data will not be able to be transferred after 10/31/2019 at 01:59 (UTC).
• All the Gems you have will no longer be usable once service has ended. We recommend that you use any Gems in your possession by 10/31/2019 at 01:59 (UTC).
• The Above dates are subject to change without warning.

We extend our deepest gratitude for your patronage.

Source: https://play.google.com/store/apps/details?id=jp.pokemon.pokemoncomaster&hl=en