I have created a number of 3D buildings using SketchUp and ArcGIS Pro which are stored as a multipatch. All buildings are visible in ArcGIS Pro and with the correct appearence. I have created a scene layer package and published to ArcGIS online. When I open the layer in a scene a number of the buildings are missing and a number have got white roofs and not the colour which I see in ArcGIS Pro. When I view the multipatch in a 2D map in Pro/Desktop/Catalog the missing buildings are visible. I don't think it has anything to do with the base elevation value as most buildings as visible.