Generally, when I'm working on an illustration, I'll build everything as vector shapes, block out colors, and then switch to Pixel Mode to add texture.
In the Pixel Persona, I'll select the shape I'm adding raster texture to using the Move tool, use the eyedropper from the Color Palette to grab the color from the shape, set the shape's color to white, clear any stroke color, switch to the Paint Brush tool, and drop the color from the eye dropper into the stroke color to use with my selected brush.
Right now, that isn't working when the Paint Brush tool is selected. (It works as expected when the Move tool is selected.) Nothing happens when I click on the color selected by the eye dropper, and all the sliders are frozen in place. (Even in the Color Wheel option.)
I can use the eye dropper and the sliders from top menu correctly, but not from the color palette.