It seems there is a bug in vCenter 6.7 which caused the update check of VCSA is not working.
So to upgrade VCSA from 6.7 to 6.7u1, you need to
1 2 | 1. In the vCenter Server Appliance Management Interface, go to Update > Settings and configure the custom URL to https://vapp-updates.vmware.com/vai-catalog/valm/vmw/8d167796-34d5-4899-be0a-6daade4005a3/6.7.0.10000.latest/. 2.Re-try the upgrade. |