After a recent MS Windows update, my Avast is down. When I point to the icon in the system tray, it still displays "You are protected". But when I open the Avast window, it just says "Avast is down" and I cannot fix it by clicking the restart button or restarting Windows.
My system is Windows 10 Home ver 1709, build 16299.125. I believe the problem happened after KB4054517.