I have been having an issue with Stadia playing in 4K, so I contacted support and we went through several items.
Internet speed; excellent
Chrome; up to date
Windows 10; up to date
Geforce Drivers; up to date
VP9 good;
Video Acceleration Information
| Decode h264 baseline | 64x64 to 4096x4096 pixels |
| Decode h264 main | 64x64 to 4096x4096 pixels |
| Decode h264 high | 64x64 to 4096x4096 pixels |
| Decode vp9 profile0 | 64x64 to 8192x8192 pixels |
| Encode h264 baseline | 0x0 to 1920x1088 pixels, and/or 30.000 fps |
| Encode h264 main | 0x0 to 1920x1088 pixels, and/or 30.000 fps |
| Encode h264 high | 0x0 to 1920x1088 pixels, and/or 30.000 fps |
I could only play up to 1080p! Would not let me choose 4k.
So, what is the issue? Support was just about to let me go. The guy really tried and talked with others while I was connected to them. I told him to hold on and let me try something. I had to close Chrome and changed my SLI mode to "Disable".
Guess what? Now I can change to 4k in Stadia! So what is going on? Is it Chrome or is it Stadia?
I think it is combination of both.
Did you try the Stadia+ unofficial extension for Chrome?
You can force the resolution with Stadia+.
Is this is a work around for you right now?
Yes, thanks. I have tried both the Stadia+ and Stadia Enhanced v1.7.0
Game will start, but never run and eventually go back to home again. It will stay locked in at 4k. As soon as I change from SLI mode enabled to disabled it works.