Hi, same problem here. The icon disappeared some months ago. And I get no notifications (e.g. for updates) anymore. The app and the virus pattern seem to be actual. I am working with a standard account in MacOS. When I am switching to my admin account, the icon is back again. Deinstall and reinstall does not solve the problem.
Avast Mac Security Pro 13.1
MacOS 10.13.1
Any ideas?