Same, CORS must be enabled on the server to make it loadable in the viewer. Among the big file share solutions DropBox works the best with the viewer.

Search for DropBox in the documentation for details:

https://3dviewer.net/info/index.html

You can find help for embedding in the developer documentation:

https://kovacsv.github.io/Online3DViewer/index.html

It uses occt-import-js that compiles only a minimal set of code from OCCT to open step, iges and brep files.

https://github.com/kovacsv/occt-import-js