Problem with Google Earth Web

Google says that not all features of KML/KMZ (and other things, probably) are available in the browser version.

https://support.google.com/earth/answer/7365595?co=GENIE.Platform%3DDesktop&hl=en

Edit.  a basic object, like a polygon, imports into Web.  But I don't think you will have much luck with more complex files.