In getting Exchange installed in our environment, I had to completely rip it out and start over. I started with mail1 and mail2 servers running the CAS/HT/MBX roles but found that I would have needed a hardware load balancer for the CAS array. After getting everything up and running in a proper configuration, I launched the Exchange Management Console from my admin workstation and the “Microsoft Exchange On-premises Server” fails to initialize because it’s trying to connect to the old mail1 server which doesn’t exist anymore. I tried uninstalling the management tools from my workstation and re-installing them. Still failed. After a hour or so of looking around I finally found out how to fix this. Delete the following key in the registry: HKCU\Software\Microsoft\Exchangeserver\v14\AdminTools\NodeStructureSettings.
Restart the EMC and you’ll be good to go.