There must be a full 2-way forest trust between all forests that contain users that will be mapped into BusinessObjects. Refer the below note for the same.
1323391 - What are the requirements to perform SSO or manual authentication from multiple AD forests in XI 3.1
Refer the below note to have check your AD Domains 2-way transitive trust.
1384606 - How To view Active Directory Trusts using Microsoft Management Console (mmc).
