Colour selection not working - Essentials 7

Hi there, I'd be incredibly grateful for some help.  I've just bought Essentials 7 and I'm having issues with the colour wheel because it isn't keeping the colour I've selected. The colour jumps to an unselected, random colour when i use my pen (Huion GT-191) on the screen to draw.  No idea why it's an issue or how to fix this.

Also when I choose the grayscale wheel and start to draw, instead of being able to draw in grayscale, the software opens up a window to place an image file.

Any help would be hugely appreciated.

Thanks in advance