Question: Recently, I've got my Xubuntu to 16.04 and I found indicators in `xfce4-panel` have a problem.

As shown in the picture below, volume indicator is missing.

[![enter image description here](https://i.stack.imgur.com/Z9k7U.png)](https://i.stack.imgur.com/Z9k7U.png)

As ugly background color, I don't want to use `xfce4-pulseaudio-plugin` and `xfce4-mixer` is unavailable.

Does anyone know how to solve this problem?

Answer: 
You might have indicator-plugin missing from the panel.

Right click on the panel and select

> 
> Panel -> Panel Preferences -> Items and click on the + button
> 
> 
> 

Search for Indicator Plugin and add it.

I hope that works.
All settings->Sound -> bottom checkbox "Show sound volume in the menu bar"