Where are you clicking on Shield Control ?
As far as I'm aware Avast Shield Control is on the avast tray icon's right click menu and isn't actually telling you of the status - more so allowing you to disable them and enable them.
So the 'All shields are on' text greyed out is telling you they are on (so the option is disabled, not the shields), only when you disable a shield/s will that text change and allow you to 'Enable all shields'
After all this time and you haven't seen this before ?