Parent Domain can't access Child Domain A/D but can ping & access files

Question

I have a primary domain XXX.com running DHCP. I have a Child domain child.xxx.com running Static IP.

In Active Directory Sites and Services I have both DCs under one group. I am able to ping and access files from the Primary DC to the Child DC.

Main problem is I can't access the Active Directory from my primary domain control for the Child domain. In my server manager I can see the server but it says "Kerberos authentication error." Both servers are running Windows Server 2016.

I tried to setup the child on a DHCP subnet but when it didn't work I put the server back in to the group in ADSS.

I am afraid I broke some kind of trust that I can't fix. I am looking to at least get communication back before I figure out my subnet problem. What did I forget to change so that I can access my child A/D from my parent DC?

Answer 1

Found an issue where I moved the child domain DC out of the Site in Sites & Services and the DNS records were missing in DNS. I moved the child DC back in and remade the records and all is talking again.