How do I re-link the File Provider Dropbox folder?

Hi, 

I upgraded to the new file provider dropbox a few months ago.  In the last few weeks, dropbox didn't seem to be syncing, even after I clicked move to online only and my hard-drive suddenly filled up leading to mac warning signs.  

So I logged out then back in.  When I logged back in, I found that dropbox had "unlinked" my file provider folder.  It had forgotten that I had done the file provider update and made a new blank old-style dropbox folder, which it is trying to start resyncing everything.

The trouble is, I don't have enough hard-drive space to enable it to fully resync, and I'm worried that there might be data in the file-provider folder that never actually synced to dropbox online, so I can't delete anything.  And it won't let me re-update to file provider until everything is synced.  Which it can't because of the lack of harddrive space. 

Finally, the nature of my work means that I have more than 500,000 files and so I had all my settings setup to avoid that trap, but dropbox also seems to have forgotten that. And I can't edit them until it's synced.

Given that 10 minutes ago, everything seemed to be working fine (or maybe not given the potential lack of syncing), I'm pretty frustrated.

How can I simply re-link my file provider folder so that I don't lose anything or have to resync 500Gb?   Or any other suggestions to get me out of this catch 22?   Any advice would be very welcome. 

Many thanks, Helen