By default only COM1 and COM2 can be enabled for a VM. This site describes the problem better than me: kb.vmware.com/s/article/1002463
However to enable COM3 for a VM you need to do it manually. Open up your VMs .vmx file and add the following lines:
serial2.present = "TRUE" serial2.fileName = "COM3" serial2.startConnected = "TRUE"
- For COM4 you can do the same, just make sure you change serial2 to serial3 and COM3 to COM4.