I am adding a 2019 DC to my existing 2012R2 Single server domain in hopes to retire the 2012R2. I have added the 2019 to the domain and am in the process of promoting it do a DC and am getting an error of:
"Verification of replica failed. The forest functional level is not supported. To install a Windows Server 2019 domain or domain controller, the forest functional level must be Windows Server 2008 or higher."
I have checked and the level shows that the functional level of the 2012R2 is set to 2012. I have the primary DNS of the new server pointing to the old server, I have run DCDiag on the old server with no errors, and I am not getting any events in the logs that appear to be connected to my issue. Is there a "gotcha" that I may be missing?