I cannot use the hue cube or swatches tab to select colors.

Hopefully I'm not posting to the wrong place, this is my first time here. 

So here's my problem. I'm running Photoshop CC 2020, I believe. Everything has been fine for months, maybe over a year, until now. I was using the brush tool and selecting colors when suddenly the color I'm using doesn't change to the one I need. I keep on selecting different colors from the hue cube or my swatches group. But the color stays the same. I realize I can change the color by using the eyedropper tool and selecting colors I'd already used, but it's difficult to get exact colors and I can't use any new colors not already in my work. 

I can't seem to find a post about this. Is there a solution?