No audio output to TV via HDMI?

I recently bought a skeeball machine and replaced the electronics with a PC and a 27.5" tv. I’ve written SkeeBall game software in MonoGame and am trying to get it running on the machine.

When I hook my computer up to a TV via audio out, there is no game audio. Oddly enough however, system event sounds play on the TV just fine. I’ve already triplechecked that the LG TV HDMI audio out is set as the default playback device on windows. The only thing that seems to not want to output sound on the TV itself is the monogame app.

Any suggestions?