Fixing a Flat or Missing 3D Sun and Moon

Rule Out Pack Conflicts First

A flat sun is almost always a pack-order problem, not a bug. Open Options → Resource Packs and look at the *Selected* list. Any pack that also ships sun.png or moon_phases.png will override the cubes if it sits above Cubic Sun & Moon. Drag Cubic Sun & Moon to the very top and press Done.

Check the Usual Suspects

If reordering does not help, work through these:

• Shader packs replace the sky rendering entirely. Disable your shader in *Video Settings → Shaders* and look at the sky again. If the cubes return, the shader is the conflict — either drop the shader or choose one that leaves celestial textures alone.
• Other sky mods that add custom suns, moons, or skyboxes can fight the pack. Temporarily remove them to confirm.
• OptiFine or a rendering mod with its own sun/moon toggle can suppress the cubes. Make sure any "custom sun/moon" option is left at default.

Force a Clean Reload

After every change, reload resources with F3 + T rather than quitting. If the sky is still flat, back out to the title screen, re-enter the world, and check at both sunrise and night — the moon phases are separate textures, so a broken moon with a working sun points at a specific file conflict rather than a global failure.