Since I couldn't figure out this during beta test since I didn't get any AOS because it still doesn't work in Firefox 64bit, I've noticed it now after downloading AOS add-on from my.avast.com page.
If I only have one Firefox window open, clicking AOS button opens the side panel. But if I open new windows (not new tabs, new windows!), clicking add-on button doesn't work, but only in newly created windows. It still works in original window, but not in any newly created one.
I usually use such configuration when I'm watching Youtube or Twitch while browsing the internet with windows side by side and it is quite annoying...
