Hi gelmir, glad you liked the game!
This error usually indicates that something has prevented your sound device from initalizing. It could be an issue with the sound driver that's being automatically selected by the config file, in which case you would have to select one manually, or in some cases it's also been reported that it can happen if the game is installed to a folder with extended ASCII or Unicode characters.
You can see the possible solutions in more detail a few comments below, in case you're interested: https://itch.io/post/3576064. In any case, when we publish the new version with the DLC both here and on Steam in September, I will provide a troubleshooting document for anybody who might run into this issue.