Make sure you are connected to a stable internet connection
DomiNations is a mobile game that requires a steady internet connection in order to play. Loss of connection may occur for a number of reasons that exist beyond our control. Make that you on a stable WiFi connection. Switching connection types from WiFi to cellular, or vice versa may also help. If the problem persists, you may want to follow up with your internet provider to explore more reliable and faster connection options.
As a last resort, reinstalling the game ensures that you are running the latest version of the game, and possibly fixes corrupted files in your game client. You will not lose your game progress as long as your account is linked to Google Play.