When sharing a web scene layer or a web scene, the coordinate system of the scene is used. The spatial reference of the scene or elevation surface is not supported.
When sharing a local 
scene as a web scene to ArcGIS Online, the only supported geographic coordinate system is WGS 1984. Projected coordinate systems are supported when sharing local scenes to ArcGIS Online or ArcGIS Enterprise. In a global 
scene, China Geodetic Coordinate System 2000 is not supported when sharing a web scene prior to ArcGIS Enterprise 10.8.
Custom coordinate systems are not supported when sharing a web scene prior to ArcGIS Enterprise 10.9.
Solutions
Do one of the following:
- If the local scene is in WGS 1984 or China Geodetic Coordinate System 2000, change the local scene to a global scene. On the View tab, in the View group, click Global .
- Change the spatial reference of the scene to a supported coordinate system that has a Well Known ID.
More information
For more information, see Specify a coordinate system and Analyze your GIS resource.