Audio problems: Music works, no other sounds do

Girlfriend and I are trying to play a match of LAN; but she can't hear anything other than the music.

Tinkered with every in-game setting, updated drivers, nothing seems to work.

We came across a post with the same problem as us on this subreddit, from 3 years ago. It didn't have any replies, so I'm making this new post to see if anyone has any ideas.