The Dropbox issue has been resolved by the Dropbox team. You should be able to log in to the App. without error now.
Please let us know if you continue to experience trouble logging in.
This is currently being investigated, but the login issue seems be on the Dropbox side. We have reached out to them and are waiting for their response. I will update you as soon as we have additional information.
This problem has been occurring for a client since Monday the 26th. Previous posts suggest this was due to an authentication problem on a server controlled by Xerox. If this is correct, can someone fix it?