I found the. The inner cloud sphere object had both static and dynamic shadows checked inside the Blueprint Component. If you uncheck the Dynamic Shadows option it fixes the problem.
I have another question however… how do you change the default moon mesh? I thought it would simply be to replace it inside the Blueprint but for some reason its still using your mesh. I even tried re-importing my own mesh as a replacement for the moon model but its still using the original somehow.
Finally would it also be possible for you to put together a simple tutorial showing how to adjust the various values of the blueprint via the level blueprint so we can turn lightning on and off, increase and decrease cloud opacity, cloud speed etc. at various times?