I reinstalled ASB and the video downloader extension now appears, and when activated, a small black rectangular box with arrow icon appears. However, when selected, as might be expected, the downloader reports 'There are no videos to download on this page' - tried several Youtube videos with the same result. Personally, I think that when the Avast downloader works, it's the best of the bunch (including paid versions with all the accompanying mostly useless extra features) Avast's downloader was simple and easy to use - if only they could get it to work consistently.