Dropbox recently changed the way they handle symlinks.
Only files and folders in your computer’s Dropbox folder will be backed up
For example, if you have a symlink in Dropbox that links to a folder outside
Dropbox, we won’t back up that folder that’s outside of Dropbox. So on
www.dropbox.com you’ll just see a symlink—not a folder.
What does work now is to move the User directory into the Dropbox on the first machine, then create the link in the Packages folder, same as for the other machines.
Dropbox recently changed the way they handle symlinks.
See https://help.dropbox.com/installs-integrations/sync-uploads/symlinks.
That means the guide https://packagecontrol.io/docs/syncing#dropbox-windows no longer works.
What does work now is to move the User directory into the Dropbox on the first machine, then create the link in the Packages folder, same as for the other machines.