i don’t know because there are error. thank
Try deleting the MathExpression node (the bottom right really wide node that isn’t connected to the others). Did you add that on purpose? It is not required for a basic day/night cycle so delete it and try to re-compile the blueprint.
Try following tutorial for a day/night cycle: A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums
-Moving thread to the Blueprint Visual Scripting section-