Hi...
First off make sure the object is a polygone and that the edges are turly intersecting through each other. If its still not working go to Edit Polygons> normals and select> conform >then set to face then try again..
If that dont work either post up the MB file and I'll take a look, booleans are very feniky some times.
Kurt
I am enough of an artist to draw freely upon my imagination, knowledge is limited, imagination encircles the world. (Albert Einstein)
https://www.artstation.com/kurtb