Got it.
The old IP address can be viewed in the vCenter's Managed Object Browser (https://<vcenter>/mob/?moid=ExtensionManager&doPath=extensionList%5b%22com%2enetapp%2eaegis%22%5d%2eclient).
It actually show up in both com.netapp.aegis and com.netapp.scvm.webclient extensions, and in both the client and server URL string.
Couldn't find a simple way to update those URLs, so I just unregistered the plugins, and registered them again from https://<snapcenter_ip>:8144/register.html.
Problem fixed !