This Knowledgebase article provides a workaround for starting the vCenter Server 6.x services on the active server when VMware Service Lifecycle Manager (vmon) service fails to start its child vCenter Services (for unknown reason).
Starting with vSphere 6.5, the vCenter Server services run as child processes of the VMware Service Lifecycle Manager service. If a vCenter Service service fails, VMware Service Lifecycle Manager restarts it. VMware Service Lifecycle Manager monitors the health of services and it takes preconfigured remediation action when it detects a failure. Service does not restart if multiple attempts to remediate fail.
When vCenter Server services are starting, some of the plugin’s vCenter Server application availability rules fail.
Some of the vCenter Server services are not running: VMware Service Lifecycle Manager fails to start them for some unknown reason. This can be checked by opening an administrative command prompt on the local vCenter Server and execute the following commands:
cd C:\Program Files\VMware\vCenter Server\bin
service-control --status
Solution 1: from Neverfail Engine Management Service or Advanced Management Client: stop applications followed by a start applications
Solution 2: open an administrative command prompt and execute the following commands:
cd C:\Program Files\VMware\vCenter Server\bin
service-control --start --all
More details about how to stop, start, or restart vCenter Server 6.x services are presented in VMware KB How to stop, start, or restart vCenter Server 6.x services (2109881).
Neverfail Engine v8.1 or higher
How to stop, start, or restart vCenter Server 6.x services (2109881).
KBID-3025