This issue is seen during SDDC Manager deployments. During the "Create Transport Node Collection" task in the SDDC Manager bringup, a failure message is thrown:
"Failed to monitor bring-up process: Http failure response for /api/v1/sddcs: 0 Unknown Error"
This issue happens when NTP settings are not configured, or when the NSX components cannot reach the NTP servers during SDDC Manager bringup.
Reconfigure the NTP settings in NSX so that reachable NTP servers are used.
Click "Retry" on the failing SDDC Manager bringup page.