In addition to the Fault Tolerant VM failing to start, there are errors reported in vSphere client for PowerChute Network Shutdown (PowerChute) attempting to start a secondary VM.
PowerChute Network Shutdown v3.1, 4.x
This issue occurs if the vCenter Server goes offline during a shutdown sequence. PowerChute then fails to identify which VM is the primary and which is the secondary.
None. When vCenter Server becomes accessible, PowerChute will be able to identify the primary VM and issue a startup command to it. The secondary VM will be started by the system.