If you noticed that you're not earning any coins, it's possible that you are playing under the 'tournament mode'. In this mode, you won't be earning any coins but 'crowns'

To switch back to the classic mode and earn coins (instead of crowns), please go back to the home page (tap settings/cog icon) and tap on the big play button.

If the above doesn't apply in your case, please send us a screen recording of your game so we can check the issue further.  Thank you.