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Long story short. We have a 2012 R2 ADFS Server. We want to upgrade to 2019 and started going through the process of adding the 2019 server to the 2012 Farm. Each time we go to join we get an ADMIN0012 Error. We even attempted to add node through Powershell and get the same issue with a little bit more information "Unable to synchronize local database". We attempted to add a 2016 server with same issues. However, when we added a 2012 R2 Server to see if that worked it joined with no problems. So now have two 2012 R2 Servers in farm....but no closer to adding 2019 to eventually get off the 2012 Servers. Any suggestion would be helpful....