How to register Exchange server 2016 keys with powershell

Some time you may be unable to enter the Exchange server 2016 product key from ECP/EAC.

As i faced the same. i migrated an exchange environment from exchange server 2013 to exchange 2016. the ECP was still pointing to the exchange server 2013 CAS server. so when i tried to enter the product from ECP i was getting an error like as below

"An error occurred while accessing the registry on the server "Servername". The error that occurred is: "The network path was not found. "."

And the reason might be that the virtual directory i.e (https://mail.domain.com/ECP) was still pointing to the 2013 CAS servers.

So then i tried to put/enter the key through power shell as below and i was able to register the server in this way.

  

Set-ExchangeServer -Identity ServerName -ProductKey 8JHUYI-JHUYM-VNMFE-FGHJY-HJYUTV

So per my experience, if you want to register the key for the 2016 through ECP (https://mail.domain.com/ECP), your required virtual directory should be pointing to that 2016 environment/server.