Solution:  Make sure touse the clone stamp tool correctly. 

How are you using the clone stamp tool?   Correct layer selected?  ALT + click on what you want to clone?

Is the little blue box surrounding the layer thumbnail you want to clone stuff on?

You can’t use the clone tool on adjust layers or blank layers. 

Stuff like that.    

A screenshot of the entire program (like what you see below) when you see this message would help.