Official comment
The KMZ model was pretty hard for the desktop version to load. It always took 10+ seconds to load and was right at the edge of what it would accept. I am not familiar with the web version of Google Earth but would imagine it is less capable than the desktop version, not more capable. It sounds like Google Earth's web version doesn't accept 3D models, at least not complex ones like the ones produced with Maps Made Easy that are intended to be opened on the desktop version.
If you are looking for an online way to view the 3D model we recommend using Sketchfab.