Hard Down: Windows server 2019 active directory unable to start

Question

After a DC demotion the domain is no longer available.
After to run ADSI edit and see the domain
The response when attempting to start active directory domain services is naming information cannot be located because the specified domain either does not exist or could not be contacted.
DNS looks clean.

Answer 1

I think its a lost cause because health was not 100% before beginning the process. My suggestion is to turn off the 2019, restore the 2012 from a recent backup then follow along below.

The two prerequisites to introducing the first 2019 domain controller are that domain functional level needs to be 2008 or higher and older sysvol FRS replication needs to have been migrated to DFSR
https://techcommunity.microsoft.com/t5/Storage-at-Microsoft/Streamlined-Migration-of-FRS-to-DFSR-SYSVOL/ba-p/425405

I'd use dcdiag / repadmin tools to verify health correcting all errors found before starting any operations. Then stand up the new 2019, patch it fully, license it, join existing domain, add active directory domain services, promote it also making it a GC (recommended), transfer FSMO roles over (optional), transfer pdc emulator role (optional), use dcdiag / repadmin tools to again verify health, when all is good you can decommission / demote old one.

--please don't forget to Accept as answer if the reply is helpful--

Answer 2

Please run;

Dcdiag /v /c /d /e /s:%computername% >c:\dcdiag.log
repadmin /showrepl >C:\repl.txt
ipconfig /all > C:\dc1.txt
ipconfig /all > C:\dc2.txt

then put unzipped text files up on OneDrive and share a link.

Answer 3

What was the OS of demoted domain controller? Had the FRS->DFS migration been performed? Are sysvol and netlogon shares present on new one?

Answer 4

There was not a procedure of FRS - DFS migration

Does this mean it was already confirmed to be DFS?

I'd check the Global Catalog is checked

Answer 5

Something here may help.
https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/troubleshoot-missing-sysvol-and-netlogon-shares

What errors are present in the event log?