Tools and Adjustment

[Wolfgang Brenner]

For example: If you try to use canal mixer or black&white etc. this window opens to adjust. if you don´t close and you open another window on tools (like perpective  or stamp for clone) this will not work. 

[Old Bruce]

I think what is happening is that you have the Adjustment layer selected (which means the Alpha mask for that layer) and so there is nothing for the Clone Stamp tool to use. You must select the Image or Pixel layer in the layers pane to have the tool work. You are trying to clone an empty layer onto an empty layer. You could also select the Current Layer and Below or the Layers beneath in the Context toolbar.