I'm having a weird problem with WingPanel. The network indicator isn't present at all and used to be, and I'm not seeing my other tray items as I should be.
I should be seeing the network dropdown and Skype, Syncthing, Dropbox, etc., but I see nothing. I'm on a pretty fresh install of Freya, and I'm up to date on all packages as of right now.
This is a possible solution, I am not sure whether it is exact solution or not
(please comment if you want to downvote).
The possible reason for Indicators and icons missing in WIngPanel is:
sometimes dependencies are getting removed: (most of the cases these are the culprits )
indicator-application
xdg-user-dirs
xdg-user-dirs-gtk
Open terminal and run the command:
sudo apt-get install indicator-application xdg-user-dirs xdg-user-dirs-gtk
sudo apt-get install indicator-application xdg-user-dirs xdg-user-dirs-gtkindicator-applicationwas uninstalled and it now seems to work.