I am using PCB Editor. My blind and buried vias are not stacking even though I have set Min BBVia Gap = 0


In addition to the stagger distance, vias are also controlled by the physical constraint for Pad to Pad Connect. 

Check your physical constraints for those nets with vias that you want to stack. Vias are allowed to stack when vias are allowed in the Pad to Pad Connect. 

ALL_ALLOWED or VIAS_VIAS_ONLY allows the blind and buried vias to stack.