Resetting root account password of vCenter Server ...
https://kb.vmware.com/s/article/206904113.05.2021 · Note: If the root account is not accessible through the console like secure shell and the Virtual Appliance Management Interface (VAMI) (vCenter Server Appliance 6.0 Update 1) then that indicates that the root account is inactivated due to password expiration.. Reactivate Account and Modify Kernel option in GRUB: Reboot the vCenter Server appliance using the vSphere Client.