It seems that your game may be disconnected from Google Play.
1. Go to Game Settings (the "⚙" icon in the top-right corner) and open the "Account" tab.
2. Tap the slider near the gamepad icon. You'll see a pop-up window. If you have more than one Google Play account, please choose the one that you used before.
3. Reload the game.
If you completed these 3 steps and your progress is still not restored, please send a message to our support team from within the game: go to Game Settings, "Support" tab and press the "Report" button.