Having trouble with intersect faces

[L i am]

Hi, I am trying to intersect a "sphere" into some simple geometry but it is not working for me as per the images. does anyone have a solution?

[Box]

Without seeing the model my guess would a scale issue. Related to the tiny face issue.
The more detailed the Sphere the shorter the edges become the more likely the edges are to fail to form.
But by scaling up you may get it to work. Failing that you can draw in the missing edges.

[L i am]

Thanks as usual Box I scaled it up by a factor of 10, worked like a charm