Why can't I adjust brightness of my external LG 5k ultrafine?

I can no longer adjust the brightness of my LG 5k ultrafine display that I bought from the Apple store. The buttons on the keyboard do nothing, and when I open display setting, the brightness slider is missing. I have a M1 max MacBook pro 16". I just upgraded to 12.5.1. Unplugging the LG display power, thunderbolt cable, rebooting, etc etc. Nothing works. Can someone help??? My bightness is stuck at 50% and its terrible. When my Mac display is on (not in clamshell mode) then I can adjust the MacBook display just fine, but not the LG display, no matter what I do. Please help!