Select that first one row and change the At least. You cannot simply drag a bottom of row down when it is set to At Least. You might try to set it to Exactly some value
Your example table has only one row and its "At Least" height is set to 323mm (about 12 inches). If you try to drag the bottom edge down (which means add a row) the resulting row is too tall for the page; so the overly tall row will not show.
Try changing the "At Least" height to something smaller.