If the developer of the project is not answering, there is not really anyone else that can help fix the issue of their game.
Assuming the bug is a minor issue with the game, then the only thing you could do is let the developer know, as you did. It’s now up to them to decide if they want to do anything about it or not. If it’s a game-breaking bug that makes the game un-playable, you could request a refund, but that depends on the project’s state.