Sorry you guys, I forgot about this.
I tested my keyboard, turns out it registers all the other input combinations, except that one... The problem is my keyboard.
Thank you.
"Ctrl + Shift + U" does not apply "Hue/Saturation". This is infuriating, as I sometimes have to apply effects to about 25+ images in a row. I use all the other hotkeys to do this task very quickly. Not sure if there's a reason, I'm just pointing it out.