Sure no problem, thanks for responding.
I figured out the problem and sccm clients are now receiving certificates and clients are manageable from the sccm console.
However first of all, let me reply to your response-
I have correctly configured Forest Discovery and published SCCM site information. I see under Administration>Hierarchy Configuration>Active Directory Forests Discovery Status and Publishing status as succeeded.
Now after digging through IIS logs on MP server and client install logs, we noticed the client gets an unauthorized error message. I found out the root of the problem is the MP server on domain B needed the setting enabled "require the site server to initiate connections to this site system"
after that setting was enabled, SCCM clients in Domain B are now receiving certificates and it all now works.