Similar problem. Just created simple model of a water tank, geo-located in SU 2020 Pro. Using most recent Placemaker for the surrounding buildings. Exported file to a KMZ. Opened it in Google Earth Pro. Showed everything but the “new” water tank. So, just to be crafty, I opened my SU2020 file, saved it as a SU2016 file. Then opened that in my SU2016 and added the water tank and saved it again as a SU16 file. Export the KMZ and DARN, it showed up just fine in Google Earth !
Any ideas? Do I always have to do this now since Google Earth is not supporting SU anymore?