A 504 error from Dropbox is returned in case the server timed out on your request (due to network contention or their servers experiencing heavy load). This can even happen in case Dropbox has blocked access to your account in case they feel their server is being abused by too much traffic.
Article ID: 548
Created On: Mon, Nov 28, 2011 at 5:00 PM
Last Updated On: Sun, Oct 14, 2012 at 3:08 PM
Online URL: https://www.2doapp.com/kb/article/dropbox-sync-fails-with-a-504-error.html