Child Domain Questions

I had a problem the migration of one of my NT 4 domains to a child domain. Right now the child domain is working and sees the parent domain and the trust is setup. Everything looks great from that side. The parent side on the other hand sees the child domain as an external domain. The trust is set up but it is seeing the domain as an external domain not a child. How fix this without having to revert the child domain to NT and redo the upgrade?