App Indicators not working on Ubuntu 18.04

What I did was:

1. sudo apt purge indicator-common

1. Then, you can enable either the TopIcons Plus or Ubuntu AppIndicators extension.

2. Reboot the system or just reload the Gnome Shell with Alt+F2, then r.

Then you would be able to see the icons on the GNOME's bar.

You don't have to uninstall ubuntu - appindicator. Just turning on ubuntu - appindicator first in gnome-tweak, and then install topicon plus, there are no problems.

Edit:

If you don't have it already, install the package gnome-tweaks.

Run "gnome-tweaks" and look at the 4th item called "Extensions". Looks like this:

Make sure you enable Kstatusnotifieritem/appindicator support.