Heal/Clone Brush Doesn't work

[ZZZZ20]

I can't make Heal/Clone Brush to do what it is supposed to do.  Basically, it doesn't work.  Please help! Thanks.

[seamack40]

My heal/clone brush is all wonky too...and i can't find help anywhere to get it fixed

[JohanElzenga]

Check your tool settings, such as Size, Feather and Opacity. For the second poster: define 'wonky'.