Thanks to daarbennikweer for sending me this information.
"Technology changes at Google have necessitated the removal of the 360Cities layer from the list of default layers in Google Earth. This will happen on November 5, 2019. However, working with the Google Earth team, we are producing our own KMZ file that allows you to continue exploring and enjoying our high-quality panoramas in Google Earth desktop.
Instructions on how to find this page will be available in Google Earth until January of 2020 in order to give our users time to transition"
Apparently not. Noisette is trying though. What I really miss is the old Google Earth help forum. It's full of wisdom that isn't recorded anywhere else. Google has never documented GE properly and that was the only place to go for answers. When the GEC was moved here, Google wanted to delete it but we yelled loud enough that they made it read only instead. Now a new bunch of programmers have pushed a new forum format on us called Tailwind. They deleted the help forum and the oGEC forum suddenly without asking for comments. It all means nothing to them.
The same thing was about to happen to 360 Cities but I got really loud and one of the more experienced developers listened. The new .kmz file just makes 360 Cities responsible for maintaining it instead of Google. I haven't heard a word from the 360 Cities community though. Not on the GE help forum or the 360 Cities forum. Go figure.