You need to define the Vias accordingly. Layout has 16 Via definitions only, you need to have "undefined" pads for the unused layers, for example, Top<>Pwr, Top<>Pwr<>Gnd, Bottom<>Gnd<>Pwr, Bottom<>Gnd, you may also want Pwr<>Gnd, and any other routing via requirements - you can quickly run out of vias. You can change the via used while routing, or after routing. Care needs to be take when "stacked" BB vias are created since Layout is not "real great" at handling this properly. You would probably be better to look at PCB Editor for Blind / Buried via designs since it was built to handle these "from the ground up".