Dropbox system tray icon missing, not working

Lubuntu 14.04 ....I have a few machines, all the same OS. One by one Dropbox icon dissappeared.

I have struggled for months. Couldn't recover icon. Got it now!

  1. In terminal type ... dropbox stop && dbus-launch dropbox start
  2. Follow the prompts, if any. Two of my machines responded "Dropbox not installed".
  3. sudo apt-get install dropbox
  4. Repeat line 1. Icon appeared. Didn't stay after re-boot.
  5. Repeat line 1, to get icon.
  6. Go to Preferences ...General, (Dropbox icon) and un-tick 'Start Dropbox on system startup'.
  7. Now to 'Default applications for LXSession' (menu ...Preferences)
  8. Under Autostart, un-tick any previous Dropbox attempts (these can be deleted later).
  9. Add dbus-launch dropbox start
  10. Re-boot.

There are some workarounds until the bug is fixed. The best one at this moment (working for Linux distros such as Xubuntu, Linux Mint, etc.) is:

dropbox stop && DBUS_SESSION_BUS_ADDRESS="" dropbox start

More details at another StackExchange site: Dropbox icon is not working Xubuntu 14.04 LTS 64 - Ask Ubuntu

Update:

And a more recent workaround that works for more Linux operating systems:

dropbox stop && dbus-launch dropbox start

The solution for Lubuntu 17.04 is (assuming that you have downloaded a .deb file):

1) Make a copy of Dropbox autostart file:
cp ~/.config/autostart/dropbox.desktop ~/.config/autostart/newstart_dropbox.desktop

2) Edit the file newstart_dropbox.desktop. Change the Exec= line to

Exec=dbus-launch dropbox start -i;

3) Copy the file in /usr/share/applications/dropbox.desktop to ~/.local/share/applications/:

cp /usr/share/applications/dropbox.desktop ~/.local/share/applications/

4)Edit the file that you copied to ~/.local/share/applications/ like you did in step 2. Change the Exec= line to

Exec=dbus-launch dropbox start -i

5) Disable Dropbox autostart, with the following command on terminal:

dropbox autostart n

Thanks for Andrew and the Wepup8 team for the tips.
http://www.webupd8.org/2016/06/fix-dropbox-indicator-icon-and-menu-not.html