Why aren't I able to fillet these edges?

nathanael_kucman

John_vd_Werff

There are too many edges in your selection.
Try unselecting edges 1 and 2: 

Also check if edge 1 is really needed in your model, I would expect that surface should be smooth.
Ideal would be to have only 2 edges in the fillet feature, one for the top surface and one for the bottom surface.

glen_dewsbury

Try unchecking 'tangent propagation' or 'allow edge overflow' and see what happens. That way it won't try to fillet the edge between body and neck.

S1mon

It looks like you might have selected a face by mistake. That then added all of its bounding edges include the ones that @John_vd_Werff labeled 1 & 2.