All was working just great with Windows 64 as target.
Then I tested a compilation with Android as target.
When switched back to Windows target I now get the
error message "Can't load shader 'Behind'" when I run
the program. Clean and Rebuild all have been tested.

I have tested to resinstall Esenthel but that doesn't help

I think this is something related to the engine Pak not being loaded.
Can you run debugging and verify that in InitPre EE_init the engine Pak is being loaded?

Thanks. Your answer gave me a hint.
Of some reason I had checked the "Embed Engine Data" in the Project settings ...
Can't remember I did that.. However Unchecking that solved the problem

I was just about to post this.
Embed engine data will embed the engine.pak but only 2D shaders, without support for 3D (and "Behind" shader is 3D).

You can read more about "embed engine data" when hovering the mouse cursor over that option.

Yes. Thank's