The problem? Unity does not show the notification panel. This is a big issue, since some applications reside only there,and without this applet, we can’t call them back after starting them, close them or configure them (yes, we can kill them, but this is something else).
we are going to use the command for this – there is an options for GUI, but it’s simpler.
just under the terminal, using your own username (no need for sudo or root) use this command:
gsettings set com.canonical.Unity.Panel systray-whitelist "['all']"
Now, you might see the “all” part. This does mean that you can select only certain applications to go there, if you want them.