I ran into this problem after removing my VMWare ESX servers from vCenter 6.5 and adding them to a new vCenter 6.7 appliance.
Issue was caused by the sfcbd-watchdog on the ESX servers being unable to start as there were stale lock files left behind. This service is used to monitor hardware health in the ESX server.
Enable SSH on the ESX hosts, log in as root and check if the process is running by typing "/etc/init.d/sfcbd-watchdog status". If it's stopped, try starting with "/etc/init.d/sfcbd-watchdog start". If you get a message "giving up on lock...", you have a stale lock file. Delete the file it mentions, then go and start the service.
Can we see logging?
Platform Services Controller Service Logs Reference
Also have look in the VAMI of the appliance to see if you get more information regarding the issue
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