I’ve been coming across this problem intermittently and wasn’t sure if it was user error or not… I’ll open a new image, select something, make a new layer from it (cmd-j), reselect the original image, then select the Clone tool. Generally, this will have the Clone Source from the previous image I’ve been working with, so I press the Option key to set a new Clone Source and… nothing happens. No Clone Source cursor… at least, not at first. I have to wait a while before the Clone Source cursor will appear when I press Option.
I have to use Sticky Keys to keep the Option key pressed (only have the use of one hand), if that helps…