Once a youth is registered as an adult by the council and shows up as an adult on your roster in my.scouting.org, they should update on your unit roster in Scoutbook automatically within 24 hours.
Note: Moving a Scout to the adult roster in Scoutbook can be done manually by Member Care, however when done manually it doesn’t preserve any crew or ship role; so it is preferred to wait until the registration is processed. It also does not register the new adult member.