Message: No result on combining shapes
Cause
Either
(a) you have attempted to combine some shapes (see Combine Shapes) that do not intersect,
or (b) you have subtracted shapes so that no shape will result.
What Can I Do?
 Move 
 the shapes so that they intersect.
 Move 
 the shapes so that they intersect.
 Change one of the shapes 
 to be different from the others.
 Change one of the shapes 
 to be different from the others.
If you have tried to slice using a line, ensure both ends of the line are outside the objects being sliced.