Hey all. I'm trying to follow the second tutorial here on linear gradients on an image of my own, but when I go to toggle the mask overlay as described with the O key nothing happens. I found the option to do so in the menus, but the keyboard shortcut to do so is greyed out. I'm a beginner to the software so I'm not sure what's going on. I'm using the latest version of Lightroom CC.
I'm having the same issue. I press "O" and nothing happens. It's also greyed out on my screen except instead of the option, it says "ag.develop.adjustmentbruch.toggleoverlay". Looks like a very strange bug. It's unfortunate no one has responded. Did you figure it out eventually?