I am scratching my head big time.
I have Windows 10, a 3090, and a Q90T.
But no matter how I toy with the settings, when I enable 120hz 4k I get vertical lines on the top quarter of the screen, and the rest is black.
HDMI cable is rated 48 GB/s, in port 4...all hardware connected as it should be.
I have tried with HDR on, off, game mode on, off, VRR on and off.
I bought this TV specifically to run 4k 120hz, and I'd hoping to find some help with settings to get it working.