Can't edit a layer

[Joachim Meeûs]

Hello,
I'm a absolute beginner of PS and I'm really fighting with an issue.
I opened two images : a landscape and a sky. The purpose is to delete a tree and change the sky.
The problem is, when I create a new layer and use the spot healing brush tool, nothing happens 😕 

I can use it on the background landscape but my purpose is to not dammage that immage.
Hope you'll have an answer ! 
Thank you 🙂

 

[PECourtejoie · Accepted solution]

Hi, I can't enlarge the image. Is use all layers checked in the option bar?

[Ged_Traynor · Accepted solution]

Enable this option

[Joachim Meeûs]

Thank you both !
It works now with this solution 🙂

[Jumpenjax]

I agree with Ged_Traynor. Did you try the patch tool or the clone tool? The content aware might also help in removing the tree.