• vCenter or ESXi host communication issues
• Issues with the vCenter Server operating system
  • These issues are usually with the OS as it exists in memory which may develop over time.

1. Connect to the ESXi host managing the VM and ensure that Power On and Power Off are available.
   • If the ESXi host also shows Power On and Power Off functions greyed out, see Virtual machine power on task hangs
2. If you suspect customer might want a root cause analysis of the failure later:
   • Follow Crashing a virtual machine on ESX/ESXi to collect diagnostic information before performing any further actions
3. Perform the following:
   • Restart the vCenter Server's vpxd service per How to Stop, Start or Restart vCenter Server 6.x Services
   • If the vpxd service restart does not work, reboot the vCenter Server.

Failed to power on virtual machine

Note: If your vCenter Server has been running for more than 120 days, it is best practice to perform updates to the vCenter Server OS if any are available for that vCenter Server version. This process will also require a reboot of the vCenter.

Keeping to that update regimen can reduce the occurrence of many issues such as the VM power-on/off appearing greyed out.