For some reason my adjustment brush is not working. I select the adjustment brush and nothing happens on the image and the symbol fails to appear. Furthermore, all previous adjustment symbols (done before the onset of this problem) are not appearing. I cannot do any targeted editing work to my photographs! I have turned off Lightroom and my PC several times but this has made no difference. Advice would be most welcome.
Check the brush size. It could be very small or extremely large. Try turning off the Use Graphics Processor option to see if that make any difference.