VM's set to revert and power-up are now failing as follows:

EXCEPTION while starting VM
java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because "suppressPowerOn" is null
java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because "suppressPowerOn" is null
at PluginClassLoader for vsphere-cloud//com.vmware.vim25.mo.VirtualMachineSnapshot.revertToSnapshot_Task(VirtualMachineSnapshot.java:56)
at PluginClassLoader for vsphere-cloud//com.vmware.vim25.mo.VirtualMachineSnapshot.revertToSnapshot_Task(VirtualMachineSnapshot.java:52)
at PluginClassLoader for vsphere-cloud//org.jenkinsci.plugins.vSphereCloudLauncher.launch(vSphereCloudLauncher.java:200)
at hudson.slaves.SlaveComputer.lambda$_connect$0(SlaveComputer.java:298)
at jenkins.util.ContextResettingExecutorService.lambda$wrap$1(ContextResettingExecutorService.java:41)
at jenkins.security.ImpersonatingExecutorService.lambda$wrap$1(ImpersonatingExecutorService.java:75)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
at java.base/java.lang.Thread.run(Thread.java:1583)
ERROR: Unexpected error in launching an agent. This is probably a bug in Jenkins