Add USB Device grayed out in ESXi 6.7

Team,

Any idea why "Add USB Device" would be grayed out in the VM's configuration within the ESXi Embedded Host Client?  I've tried multiple operating systems, USB 3.0 and USB 2.0 controllers, etc. but for some reason my WD Pa$$port USB HD device never shows up in the client.  I've also tried other basic USB devices.  Are there any troubleshooting steps I can take to see where the issue is?

Thanks,

Brad