Dropbox problem in Indicator applet in Gnome classic

I had the same problem and this solved the issue for me :

dropbox stop && DBUS_SESSION_BUS_ADDRESS="" dropbox start

I found the answer at : Dropbox icon is not working Xubuntu 14.04 LTS 64

EDIT : This solution seems working only for the active session. And this one works after a reboot too : https://askubuntu.com/a/737615/545036

This works for me ... above answers did not help

By default dropbox is launched on boot up so edit how it gets launched

DASH -> start ( click on Startup Applications) 

edit the Dropbox entry with this Command:

env XDG_CURRENT_DESKTOP=Unity dropbox start -i

now the dropbox menu no longer appears blank ;-)