Enabling Out Of Stock Action "sign Up For Notification"

I am trying to enable Out of stock action “sign up for notification” and have it selected. For all items I have “Track without options” selected.

Strangely, even for items with Quantity = 0 in the backend, the Qty shown on the Product main page is 1 and the “sign up for notification” action does not appear. What could the problem be?

Thanks for any insights.