Verify that all components on the vSphere network have their clocks synchronized. If the clocks on the machines in your vSphere network are not synchronized, SSL certificates, which are time-sensitive, might not be recognized as valid in communications between network machines.

Unsynchronized clocks can result in authentication problems, which can cause the installation to fail or prevent the vCenter Server Appliance vpxd service from starting.

Verify that any Windows host machine on which vCenter Server runs is synchronized with the Network Time Server (NTP) server. See the Knowledge Base article http://kb.vmware.com/kb/1318.

To synchronize ESXi clocks with an NTP server, you can use the Host Client. For information about editing the time configuration of an ESXi host, see vSphere Single Host Management.