As a longtime Mac & Lightroom user, I decided that there are a few things that I need to learn in Photoshop; for example, the Clone Stamp Tool. Although the use of the tool seems to be rather straightforward, I have an embarrassingly remedial question. First, I Option-click on the "source" to begin the clone. Releasing the the Option key, I move the "circle" onto my "target". When I attempt to paint over the target, the source pixels do not transfer. I am using an Apple trackpad & painting with a 3-finger movement. Undoubtedly, I am doing something wrong. Could someone kindly put me back on track? Thank you so much.