As mentioned above, make sure that the new set, is in the same tenant as everyone else, as call forwarding is control on a per tenant basis. If it needs to be in a different tenant, for other reasons, compare form 19's fields between the two tenants, and make the call fwd no answer and call fwd busy answer points go to the same place (the voicemail hunt group access code). Be aware that other sets, in this other tenant will then go to VM as well, so you may have to create a new tenant for the new set, if you don't want this.