Headphone mic does not work after booting Marathon

After launching Marathon from Steam, my headset mic totally stops working.

The headset still plays audio, but does not detect the mic. I tried all available mic input settings in Marathon, but none fix the issue.

If I try to join a call on Discord after launching the game, I get the error that my mic is not detected.

My mic is only after detected by Discord after closing the game and waiting a couple minutes.

If I am in a Discord call prior to launching the game, my mic works fine in game.

The headset is a SteelSeries Arctis 7. 

This is a super weird/annoying issue I have not had in any other game.