In the V3 : After a general or partial Fillet (say a on a Cube) You can't directly Shell, Inset, Offset ... a surface(s)!!! (Calcul failled)

So save and reload / Import your object! And apply the Shell, Inset...

In V4 (beta) all works fine directly! :)

(Congé = Fillet, Creux = Inset)