Indicator icons do not appear after upgrade to Ubuntu 17.10

I've encountered the same problem. I tried to remove the indicator-application-service completely, and see, the problem went away! I guess coming from 16.04 leaves some Unity-related stuff on my machine that is not only obsolete but prevents the AppIndicator extension from properly working.

What to do:

sudo apt remove indicator-application

I have the same problem with 17.10. At least the following command helps here to bring the icons back until the next reboot:

killall indicator-application-service

Edit: This workaround is running fine here without using any gnome-extension like "Topicon-plus" or "Kstatusnotifieritem/appindicator support".

As suggested here, try removing all obsolete indicators if any still present

indicator-application
indicator-appmenu
indicator-bluetooth
indicator-common
indicator-datetime
indicator-keyboard
indicator-messages
indicator-network
indicator-power
indicator-printers
indicator-session
indicator-sound
indicator-transfer
indicator-transfer-download-manager

Just execute this command in a terminal:

sudo apt purge indicator-application indicator-appmenu indicator-bluetooth indicator-common indicator-datetime indicator-keyboard indicator-messages indicator-network indicator-power indicator-printers indicator-session indicator-sound indicator-transfer indicator-transfer-download-manager

Another possible solution is delete Indicator-application autostart .desktop file. It's installed in

/etc/xdg/autostart/indicator-application.desktop

If you dont want to remove it and sometimes is using Unity 7. This made Indicator-application not start at login.

Nothing from suggested works for Shutter app in Ubuntu 18.04 as libgtk2-appindicator-perl package has been removed from main repo. To enable the Shutter indicator in Ubuntu 18.04 install libappindicator-dev:

libappindicator-dev

and Gtk2::AppIndicator perl extension:

sudo cpan -i Gtk2::AppIndicator

Restart Shutter, its indicator should appear now in system tray.

In all currently supported versions of Ubuntu open the terminal and type:

sudo apt install indicator-applet-complete 

Indicator-applet is an applet to display information from various applications consistently in the GNOME panel. This instance will load all indicators in a single panel applet.

I'm on 18.04 (upgraded from version 16).

After following other suggestions such as wiping the old indicator-* programs, and installing the "Kstatusnotifieritem extension", my icons returned -yay-

..but they went away every time the laptop went to lock/or was closed for awhile. Which is often.

Everything comes back, but you have to Alt+F2+R every time, which is annoying and also rearranges my bottom bar dock thing, and since I have many terminals open and arranged, you can imagine :x.

Anyway, this post seems to have fixed it.

Removing default [email protected] from /usr/share/gnome-shell/extensions

aka

sudo rm -r /usr/share/gnome-shell/extensions/[email protected]

I locked it with Super+L to test it - and my icons did not go away. :D

Click the nine dots on your dock.

At the search field write "tweak". You will see gnome tweak tools:

If you don't have it installed you can click it and that will open software center. You can install it from there.

After, run tweaks and go to extensions.

Just turn the appindicators on and you will have a working system tray where you can see the dropbox, telegram or other icons.

A combination of enolive's answer and amDude1848's answer seems to be necessary.

This will fix the problem in the current session:

killall indicator-application-service

And this will prevent the problem from reoccurring:

sudo apt remove indicator-application