This issue occurs when the user creates a new VM on VMware ESXi server version 6.0 and above, as the default virtual machine version is 11.
If a user chooses to create virtual machine on version 11, the serial device is not automatically created.
It must be added manually, when the VM is powered off.
Add to VM Hardware:
Device type = 'serial port
Serial port output ='Use physical serial port
Note: The VM must be powered off for the serial port to be added.