Hi Charlie, the problem is an anomaly in the vertical "side wall" area of this hole:



That surface has edges that go all the way around the hole but the underlying surface for that face is only half of the size it is supposed to be:



That looks like some kind of bug but the bug was in some prior step of construction.

I repaired the model by removing that bad face and building a new one and joining it in. The repaired model is attached and should boolean ok now.

If you happen to know how to repeat the steps to get that bad face in it please let me know.

- Michael