grouping control box not showing up

I cannot seem to find an answer to a grouping issue. I have attached a file to show the issue I am having. Which is, whenever I group a secondary level (rows in this example) and the last item is the last item of the parent group, it appears (because the dots move to the third column) to create the group but the group control box (sorry if the is not the correct term but I am talking about the +- box for expanding and collapsing a group) does not appear.

We would like to be able to collapse the sub-sub task as shown for the group 3 tasks in the "as saved" attached file. But as you can see there is no control box for the last set of sub-sub groups for tasks 1 & 2, yet the dots are in the correct column.