I see you have the Propagation mode set to TANGENCY. But the bottom end of that edge isn't tangent to anything, so the fillet stopped - just like it was supposed to.
You can try to extend the fillet, by choosing both the vertical edge and also the horizontal edge (it's highlighted in orange in your second picture).
Or you can add the horizontal fillet first, and then add the vertical one as a second fillet.
Let me know how this works for you. (I think fillets are the hardest thing to model in CATIA!)