When attempting to activating VMware HCX appliance you get an error:
"Unable to activate with the details provided. Please contact your administrator for assistance"
This can happen if you are trying to use the "VMware HCX Enterprise" License instead of "NSX Enterprise Plus (HCX Advanced)"
When going through the licensing process, use the NSX License first (EX NSX Enterprise Plus (HCX Advanced)), then add in the VMware HCX appliance license 2nd.