Follow How to check vCenter Server essential service status and dependencies to determine the service which is failing to start.
As per the diagram, in order for vmware-vpxd to start:
If any of these services are failing to start first, please search for troubleshooting articles related to them. The general article for these problems is at Error "503 Service Unavailable" when attempting to access vCenter Server vSphere Client
If vmware-vpxd is the only service failing out of this list then keep proceeding to the next section for further advice.
cat /var/log/vmkernel.log |grep "I/O latency increased" |awk '$20 >= 80000' |less
If you see very high latency, see the " performance has deteriorated" message in ESXi for more information.
If your vCenter Server has snapshot virtual disks running on it, if there are a large number of them, or if they have grown large, it can also cause a performance impact which will cause vpxd to stop running.
Snapshots might exist which are don't show up in the vCenter or ESXi GUI
Snapshot files will generally look like vmname-00000x.vmdk, where vmname is the name of the vCenter VM, and the x is the number of the snapshot.
Example: myvcenter-000001.vmdk
It is highly recommended to never keep a snapshot running on a VM for more than 3 days.
For either Appliance or Windows vCenter Servers, you can look at the virtual machines' performance history for CPU. storage, memory, and networking in the ESXi or vCenter host clients.
If there are any errors regarding resources in logs, or if the performance monitors show resources being pegged, this is suspicious for a performance or resource problem.
VPXD stands for Virtual Provisioning X Daemon. Virtual Provisioning X was the original name of the vCenter Server product. VPXD is the main service for running vCenter Server.
Error "503 Service Unavailable" when attempting to access vCenter Server vSphere Client Troubleshooting virtual machine snapshot descriptor problems
Impact/Risks: