After upgrading a workload domain vCenter Server via SDDC Manager, the Available Configuration Updates section may prompt you to apply the following update:
Register SDDC Manager as an extension in a workload domain vCenter.
This article explains the purpose of applying this configuration update.
VMware SDDC Manager 5.2
Configuration updates are post-upgrade actions recommended to align an upgraded environment with the standard configuration of a freshly deployed VCF environment.
Applying this update registers the SDDC Manager extension (plugin) with the newly upgraded workload domain vCenter Server.
For more details on applying configuration updates, refer to the official documentation: