I’m created a model on the online version but want to download and use it on my 2017 SketchUp make version on my computer, but it doesn’t give me an option to downgrade the versions back to 2017. When I use my 2017 version on my computer, it does give me this option. I really don’t want to remodel my design on the 2017 version from scratch.
You can’t save as an older file from the web version, at least not to a 6 years old version, you can use eneroth free plugin, open newer version, to be able to open skp files saved on newer versions of the program. I don’t use the web free version so I don’t know if you can export the file as collada (dae) format, if it’s possible you can do that and import it from sketchup make.