are you using steam beta?

nope. i have beta turned off. i also have family beta thing turned off as well.

check windows sound settings, disable all unused audio devices

and check windows mixer volume, make sure steam client volume is maxed

Done and still nothing

check this post and try the solution there maybe it'll help u
https://gtm.you1.cn/groups/homestream/discussions/0/1696095261012366936/?ctp=3

The same thing happens here. I was streaming a game to a friend and she told me there was no sound. I tried at home with 2 different PCs, an old one with a Gtx 970 and win10 and one with an AMD 6800xt with the same result, there is video but no sound. With Sunshine + Moonlight the sound works perfectly but it would be perfect if it would work again from Steam to Steam.