The Nest Box is Up, but Unnoticed

The nest box is now completely attached to the cage and ready for business, but not yet noticed by either Sutcliffe or Maryann. I recall that last time, it took Maryann several weeks, I think, to notice it, at which point she hopped happily in and out, and no breeding occurred until we removed our then third budgie Lola (Lola has been given away to a good family--four budgies was just too much).
We put many wondeful fresh grass seed collected on a walk, in front of the nest box, and the couple ate them, but didn't notice the box. Sutcliffe did a lot of back and forth on the perch, and made loud calls to Boo, who did the same in his cage (he also got greens). I wonder if this loud calling is to send the message, "food is here"?