I am dealing with a issue on my vSphere 6.5 server. After I use a Datastore ISO file and change the CD/DVD Drive 1 back to 'Host device, not connected at power on' the task Reconfig VM directly ends up with "Failed - The operation is not allowed in the current state". After this I can't manage the VM anymore through the webinterface, even the power on function is not working after this.
I have to unregister the VM and re-register it to power it on or edit the settings after this.
The problem is reproducible on my host and occurs with Windows and Linux guests. It happened on a fresh 6.5.0 installation and still is happening on ESXi-6.5.0-4564106
My host doesn't have a cdrom drive, maybe this has something to do with it.