My attempts to upgrade to vCSA 7.0, using 7.0U3h ISO (vcsa-ui-installer wizard), from vCSA 6.7 U3s fail at Stage 2 Pre-upgrade check, with error "Could not authenticate to source appliance OS on address xxx. Verify that source appliance OS credentials are correct."
I have tried multiple times/ways to change either or both the source vCSA's root password and administrator@vsphere.local password, as well as disable the password policy, but still unable to resolve this error. I'm fairly certain that the passwords are correct, because I'm able to use them to log on to the vCSA 6.7; and when I intentionally entered any wrong passwords, I would get different Pre-upgrade check error messages such as "Invalid SSO credentials for source appliance...Cannot complete login due to an incorrect username or password." or "Invalid root credentials for source appliance.....Authentication failed.
Any ideas on how to troubleshoot this is much appreciated.