Whenever new publication is created, “Changed BluePrint Hierarchy” is visible for all promotions which have “Include child Publications” and new Publication should be included in this list.
In this case, XO Promotions are not updated automatically, so the Content Editors must open each of them and just perform “Save and close”. During this action XO module will perform the update under the hood, but this can be a tedious and time-consuming task for the editors, especially when there are hundreds of Promotions.
Suggestion is to do this OOB.