Doesn't work with FF 20 - not even the add-on beta Rated 1 out of 5 stars

I tried this add-on - first standard, then beta (0.6b3) - on two computers with Win 7 / FF 20: no go. Pressing the keyboard short cut - nothing happens. Firefox menu: shows "Restart" option alright (in active black), but selecting it won't do anything.DoPo's advice (disable, then re-enable notifications): that's too vague, don't know how to do that (where's that options menu supposed to be?).Seems to me that this add-on isn't supported any more => only one star. If I find out how to make this work, I may happily reconsider.