I just subscribed stadia.
And im not able to get 4k 5.1 Sorround.
I go to the options and Performance, and i get "Up to 1080p" selected, the 4k is gray and i cant select it.
Plus i dont feel the game i tarted "Dead by daylight" is at 1080p, it looks like a 480p UTube clip.
My internet speed is 500Mb Down 100Mb Up and im using cable not Wi-Fi
16DDR4 on an I5 8600k @5.1Ghz
On a ASUS ROG Strix Z370-F Gaming Board
RTX 2080
Dont think its and hardware bottleneck from my side. So has to be something from server side.
It sounds like you're trying to play using Chrome since you posted your PC specs. The 4K option won't be available for selection officially unless you actually have a 4K display, and set to the 4K resolution. Your RTX 2080 definitely has VP9 support, so that shouldn't be an issue.
You're sure you have an active Stadia Pro subscription? On the Stadia site, you shouldn't see a "Get Stadia Pro" banner at the top, and if you check Settings/Subscriptions it should show you have an active subscription there.