This issue is caused by a data inconsistency between the VCFA (VMware Cloud Foundation 9 - Automation) and VC (vCenter) environments. The sequence of events leading to this is typically:
A region was created in VCFA and associated with a specific VKS Supervisor.
Later, that VKS Supervisor was deleted directly within VC.
A new VKS Supervisor was then created in VC.
The original region entity in VCFA was not updated or removed, so it still holds a "stale" reference to the old, deleted supervisor.
Because the region configuration points to a non-existent supervisor, the system cannot correctly associate the new supervisor with it, making it unavailable during Region Quota creation.
Customer created a region with supervisor in VCFA. Later, in VC, they deleted the supervisor and created new one without cleaning the region entity in VCFA.
To resolve this issue, you must remove the stale region configuration and create a new one that correctly points to the active VKS Supervisor.