Hi, when you say you assigned the task to the milestone you mean going to the tasks edit view, clicking on the More category, and selecting the milestone from the dropdown, right? If the task is assigned to the milestone this is shown on the header of the task's view, below its complete status. If the milestone's there and the task matches all the filters in the tasks page, and you still can't see it below the (expanded) milestone on the tasks panel, then there's a bug and we would be glad if you could help us figure it out so we can fix it.
About milestones on the Overview panel, the filters from the task panel don't affect the Overview panel. And currently the only milestones that are listed on the Overview panel are those shown on the 7 day calendar and the late ones.