After searching for hours on google and the forums; I found the solution.
- Open the file “C:\Program Files\Epic Games\UE_4.XX\Engine\Config\ConsoleVariables.ini” in any text editor.
- Find the line “; r.XGEShaderCompile = 0” and remove the “;” at the beginning of the line and delete it.
- Then just restart the editor.
After restarting the editor “Compiling Shaders” starts working properly again.