Starting in 15.6.1, there was an API naming convention change. If you need to change the API ID (for example, so you can sync the attributes in Roadmaps), the below issues happen:
STEPS TO REPRODUCE
Expected Results: Attribute still appears in the blueprint
Actual Results: Attribute no longer appears and a blank space is left where the attribute used to exist
Additionally, if the attribute was saved by users in views in the New UX, they now see error: “The selected view uses attributes that are unavailable” in the views
Release : Clarity PPM 15.6.1 and higher versions if upgrading from a prior release with old API ID Naming convention
Component : CA PPM SAAS STUDIO
Another option would be to remove everything out of the section in the blueprint with the empty space, delete the section, then recreate the section and add the fields back into the section.