If Avast tray icon disappeared, get it back easily
It is not unusual for the tray icon of Avast antivirus to disappear, even if you had selected the “always show” option in Windows taskbar properties. This can happen after you install and uninstall several programs.
The absence of the Avast tray icon doesn’t mean that the antivirus has stopped working or that it works with problems – it means only that you don’t see the icon, therefore, that you don’t see when Avast is working, checking some files for viruses.
The best way to restore the tray icon of Avast at its normal position in the system tray, is to open the Add/Remove applet of the Windows control panel, or otherwise start the uninstall dialogue of Avast, and select the Repair option.
This will fix any other problems Avast may face, and it will also reactivate the tray icon, next time you start Windows. You may like also to check this post on how to reactivate Windows Defender after you uninstall Avast.