It appears that our custom lookup mapping is gone after upgrade.
The rows still exist but the parent and child data are gone in the mappings.
Values in the specific instances are still there.
This lookup was not intended for custom use. The query which does the mapping is hard coded for the OOTB lookups Idea/Project Type and Category mappings.
Do you could check if some part of your customized query, lookups be OOTB through PPM-> Administration-> Content Add-In and take a look.
Such as this image below.
Release : 15.8.1 and above
Component : CA PPM SAAS STUDIO
Please be aware that if you create your own custom lookup mappings that upon upgrade the query will be reset and you will need to revise it again. Or do you need recreate this custom query every time that do you upgrade the PPM version.