When I started my Laptop, the taskbar icon was missing. I know how to customise it. I tried a repair from Programs and features, then a complete removal & re install + updated. Icon still missing. Action center shows Avast is ON
What other security software do you have installed, anti-spyware, etc. ?
Spybot search & destroy has a bad habit of blocking the avast startup entry for avastUI.exe.
The action center would be correct in that as avastSvc.exe is the avast process dealing with the security, the treay icon isn’t directly security related.
Only Outpost FW Pro. Could this be related http://forum.avast.com/index.php?topic=95998.new;topicseen#new
Same as me then, do you have the anti-spyware module ?
Presumably the tray icon was there before ?
In the application rules in Outpost and ensure that avastUI.exe is allowed, Network and Anti-Leak.
If it is allowed, then delete the entry for it and start avastUI.exe manually from the C:\Program Files\AVAST Software\Avast folder.
I cleared all Avast entries in Outpost before remove & reinstall. Could this http://forum.avast.com/index.php?topic=95998.new;topicseen#new be related.
I don’t believe so as that relates to BSODs not just a missing tray icon.
A few years ago the taskbar icon disappeared on me too… i just went to settings, and unchecked show avast tray icon than clicked ok… then back to settings checked it again than clicked ok… and it worked…
Problem solved, its reappeared and I did nothing to fix it.
Don’t you just love computers and their mysteries 
Seem to have heard that before.
Familiar theme all working fine one day, the next mayhem.
The Ghost in the Machine! :-X