Most of my files are showing as Zero bytes on desk top app

I have the same problem and I'm not using SmartSync for the folder in question.

I'm running Montrey 12.3.1 on a M1 Mac. I have recently updated Dropbox to the new M1 Client v147.3.4765

I have the same problem. I'm using Mac Monterey 12.13.1 and my files are showing zero bytes. 

I followed another forum comment and went to dropbox preferences, selected Account help down the option key and selected fix permissions. It fixed some. Then when i opened the files they could open and the zero bytes restored to the file size. My problem is i have 60k files so its making life a bit fo a nightmare.

 Have you checked this (option) under Settings > General > Preferences?

I was unaware of it until just now, but it does seem to answer the point. (Apple MacStudio, M1 Max, Monterey 12.5)

Have have the same issue, and I Mark's (SuperUser) comment about SmartSync is not applicable/helpful (yet somehow it is listed as the "accepted solution".  Have have 50k+ files, and most are reading Zero bytes on the desktop.  Have reinstalled the Dropbox desktop app, un-sync'd and re-sync'd the files in question, restarted Dropbox, and restarted the Macbook.  Nothing.  Has never been the case before.  Incredibly frustrating.  Hard to believe that we havent had a Dropbox employee assist with this question thread.

I found a workaround of sorts that I will share now.  The end result is that my files still do not automatically sync offline to my desktop (though that is the setting), but at least now I can open them directly in Finder (something I was not able to do prior to this fix).

Just chiming in here to say I had the same problem and then I right-clicked the main folder (from my Mac) and selected "make available offline" and that seemed to fix the issue and now all the files are actually on my desktop too.