OK, there we have it, that won't work. You'll need to enter the Retail Install Key for Professional first, then use the 'Add Feature' option and enter the Install key for ProfessionalWMC. Activate with MTK afterwards.
It will not even get me to that point. What is that CMD to change the key again. Can not change the key in control Panel
@maddog0266 Carefully follow the advice. You need to install Pro retail serial first, then upgrade to ProWMC.
After entering the Pro key, use the 'Add Feature' option and choose that you already have a key. In next window enter the ProWMC Install key and it should start the upgrade. End and save all work, as afaik it reboots automatically when done.