Maybe one of these posts can help you:
https://steamcommunity.com/app/255710/discussions/0/135511027320265206/
https://forum.unity.com/threads/no-audio-in-unity-games.532872/
Are you sure the game is not muted? Check the windows audio mixer:
https://forum.airportceo.com/t/solved-no-audio-sound-anymore/10852