Zwift mutes all sounds on Windows until OS restart

For about 2 months now, opening Zwift mutes all sounds on Windows (every application). A Windows restart is required to get sounds to be working again, until Zwift is opened again.

When launching Zwift, just when getting to the pairing screen the system sounds get a bit muffled then vanish after 2-3 seconds.

This computer doesn’t have any OS automatic update enabled. Only update was Zwift.

Manually updated sound and Nvidia drivers and tried the most common troubleshooting steps to be found on the web. Didn’t solve the issue.

OS: Windows 8.1 64-bit
Audio: Realtek High Definition Audio, latest drivers from Realtek

I’ve never had this issue. What I would say though is there’s no good reason to stay on Windows 8.1. I would recommend a clean install of Windows 10 via USB stick (not an upgrade), it’s very easy and doesn’t cost anything. There’s no need to manually install any drivers, just connect to the internet and leave Windows to it.

Thanks for your answer. Yes I agree. I was sticking to W8.1 with updates disabled in order to ensure a rock solid dedicated Zwift platform. However nowadays this results in quite the opposite effect I guess.

As a follow-up, I restored a Clonezilla image of the disk from January 2019 and updated Zwift only.
Issue appears again, which confirms this is solely due to a change on Zwift side.

And finally, as a follow-up, a clean W10 install did solve the issue.