This notification is displayed when an older device is no longer supported by the game. 

However, this notification may be wrongfully displayed on some Android devices due to a resolution set on the device. In such cases, the resolution on the device may have been lowered below the resolution required by the game.

If Google Plays notifies you that your device is incompatible, please try resetting your resolution to Mid or high in the device settings. You can do so by entering Settings -> Display -> Screen Resolution. Changing the resolution to a higher one should help resolve this issue.