Clone stamp or spot healing brush tool will not work?

Hi,

I'm not too far advanced in Photoshop, but I have been using the clone stamp and the spot healing brush to do a lot of restoration on scanned photos. Both have been working great until yesterday and they both stopped working. Then today I updated the Photoshop CC and still no luck. I tried the suggestion under the "clone stamp not working" help and none work. Can someone help me? The clone stamp does everything it supposes to but not stamp.