An OBS that has been associated to the Resource object is not listed under the 'OBS and Partitions' tab under Administration - Resources. This makes to to where we are unable to assign resources to the OBS structure.
Release : 15.7.1
Component : CA PPM Administration
The 'OBS and Partitions' tab only lists an OBS if the OBS is associated to the Resource object and it is not an OBS that is associated to an Entity. If the OBS is set to either be a Department OBS or Location OBS on an Entity (under Administration - Setup - Entities), it will not be available under Administration - Resources. It will only be available for selection under Home - Resources. Additionally, this OBS will not have it's own field, instead it will be available under the Department or Location OBS field.