The spatial reference of your web scene or web scene layer is unsupported. Unsupported spatial references include all geographic coordinate systems and custom XY and Z coordinate systems. Modifying any portion of a projection makes it custom.
Change the spatial reference of your scene to a coordinate system that has a Well Known ID.
When sharing either a web scene layer or a web scene, the projection of the scene is used. To share a web scene in WGS 1984, share the web scene or web scene layer from a global view of the scene.