Light Function issue (UE5.4)

Hello

I have an issue with Light Function

I use a directional light and want to made clouds. I did a simple material with an animate clouds and work pretty fine in the viewport.
But the problem is when i play the game, i don’t see any clouds shadows. I test with other materials and it’s the same again.

Is there a specific paramatric to tick somewhere?
Can someone help me?

Thanks!