After configuring the Desktop or Workgroup software in Ubuntu 14.04 and 16.04 running Unity, you'll get this message below if you try to get back to the Activity Monitor after closing it:
To get back to the Activity Monitor, run these three commands from terminal:
sudo apt-add-repository ppa:fixnix/indicator-systemtray-unity
sudo apt-get update
sudo apt-get install indicator-systemtray-unity
After that, logout of the system then log back in. You should know see a down arrow in the top right hand side of the screen:
From the down arrow, once Jungle Disk is running, you can access the Activity Monitor (in the screenshot above, it's the icon on the left).