Can't promote Server 2019

These two things - the error stating that a DC for the domain couldn't be located and an inability to ping existing DCs by name - do indeed suggest that you've got a DNS problem. Can you check DNS on one of the existing DCs to see whether the expected zones and records are present? This article gives an overview of the DNS records you should find.

Yes, DNS is functioning correctly on the other DCs.

If you use nslookup to send DNS queries to the existing DCs from the server that can't be promoted, are you able to get responses?

Yes; that (and pings) works.  BACSDC02 to CBLSDC01.

The domain.png screenshot shows that it was looking for a domain controller in the domain "10.100.1.14" rather than the actual domain name. Do you know what caused that?

I’m thinking the host file entries. Without that, I can’t ping by DNS name.

Can you remove the host file entries, flush the resolver cache (ipconfig /flushdns) and try promoting again? Please post the resulting error, as its description section contains a lot of information that could be useful.

Completed as per your request.
error.txt

It tells you that it cannot find the SRV records. Look in the DNS zone for your domain and make sure you see the SRV records. Should be 4 folders called. _msdcs, _Sites,_UDP, _TCP, and perhaps _DomainDNSZones. Each of these will hold SRV records for your domain. IF they are missing, make sure the Zone will accept updates and then restart the netlogon service of a functioning DC that has that DNS server as its primary.

All of those folders are located there.  See attachment.
Untitled.png

And do they have SRV records for your active DCs?

Yes, that’s correct.

Ah, I think I see the problem in that latest screenshot. Since you've got a separate forward lookup zone for _msdcs.ascendlearning.org, the _msdcs folder inside the ascendlearning.org zone shouldn't contain anything. In fact, it should be a delegation instead of an actual folder/subdomain. A delegation will appear in the console as a gray folder, which is how I can tell it's not one currently.

To properly fix this, you'll need to delete that _msdcs folder, recreate it as a delegation (right-click the ascendlearning.org zone, select New > Delegation, and follow the prompts), and then have your DCs re-register their DNS records (ipconfig /flushdns, ipconfig /registerdns, and restart the Netlogon service for the SRV records). That may sound a little scary, since you're deleting stuff along with that folder, but if everything else is working, the deleted records will reappear in the _msdcs.ascendlearning.org zone where they belong.

Same result.  See attachments.
new-error.txt
DNS-entries.PNG

Expand that _msdcs.ascendlearning.org zone, then expand dc and _tcp. Is there at least one SRV record named _ldap there?

See attachment.
DNS-entries2.PNG

If you were referring to the _msdcs.ascendlearning.org zone above the ascendlearning.org zone, then there are a number of SRV records named _ldap

Any thoughts?

Could part of the issue be that when I do an nslookup of my domain name on this DC (CBLSDC01), it returns the IP addresses of our website, under non-authoritative answer?

Could part of the issue be that when I do an nslookup of my domain name on this DC (CBLSDC01), it returns the IP addresses of our website, under non-authoritative answer?

That shouldn't cause this issue; the modern DC locator process doesn't use those records, which are there for legacy purposes. It's still not really a good thing to mess with them, though. When you do an nslookup for the domain name, you should receive only host records for your DCs.

If you were referring to the _msdcs.ascendlearning.org zone above the ascendlearning.org zone, then there are a number of SRV records named _ldap

Yep, that's the zone I'm referring to. Can you post a screenshot showing those records?