I'm running Dropbox version v96.4.172 on Mac OS Catalina (10.15.4) - iMac. I have the same OS setup on a Macbook where it works fine.
I tried reinstalling Dropbox several times, restarting the computer and removing /Library/Dropbox* and ~/.dropbox/* files. I even unlinked the computer and linked it again.
1) Dropbox sync my files if I manually pause syncing and resume syncing. But it does not sync my files if they change or get added. When I add a file (or change it), Dropbox does not upload it. If I pause and resume, the file is uploaded immediately.
2) The finder integration is different on iMac than it is on Macbook. The only finder integrations I see are:
a) Dropbox folder in sidebar
b) Open dropbox folder toolbar icon
c) Send with Transfer context menu item
There are no Sharing context menu items present (they are on Macbook).
If I add a file on a Macbook, it syncs to iMac and I see a notification. But the files from iMac are not "picked up" - like it wouldn't detect the changes?
For what it's worth, I'm running Backblaze backup on Mac, but that's about the only difference I can think of. I tried setting Backblaze backup to "on demand backup" instead of "continously", but there were no changes.