I'm running Lightroom Classic v10.3 on an iMac running Mojave v10.14.6. I've never had any problems with the adjustment brush until now. When I select the tool and beging painting my adjustment, the image only lightens where I've brushed. I've reset the brush, restarted the app and rebooted the computer with no resolution of the problem. Any help would be greatly appreciated.
Somehow, my brush overlay color was changed to white. I always use red or green depending on the image. I have no idea how it got changed to white. Nevertheless, thanks for your suggestions. The culprit was the overlay color. 👍🏼
Did you modify the sliders before clicking on the image? Otherwise the brush settings are just what they were last time you did so. If you never preload the brush like that, then all sliders are at default, and accomplish nothing until you change them.
Some people like to preload the brush that way, then paint. Others paint, then alter the sliders.