My laptop doesn't show up in my connected devices list, even though it's syncing files

I've been having so much trouble with Dropbox. Dropbox used to sync my whole computer – I could see the little icons on the files in my Finder, not just files in my local Dropbox folder on Finder. It was super convenient to manage files on my computer and I loved how I could set things to "online-only" to save device storage. One day though, all the icons had disappeared, my computer suddenly filled up (because I guess they were no longer set as online only and all started taking up storage on my device), and I learned a new "Backup" feature had been introduced. 

I've tried everything – I've chatted with a few agents who said if I backed up my whole computer I'd be able to get those icons back and things would be back to the way they used to be. I did back up my whole computer to Dropbox (in the app dropdown it says 'Everything is up to date' / under Backups there's a green "Done"). When I click "View backed up files" though, I see my Mac marked with "Unlinked" under its status. The chat agent asked me to send an email because I need extra help, but no one has replied for 15 days and somehow my ticket was marked as closed.

This problem is making everything a headache – I can barely use apps on my computer because of all the storage suddenly being used up. I can't seem to get any personalized support from Dropbox. This is my last resort – please help.