To troubleshoot a cross-domain authentication issues, the following steps may need to be taken:
- Verify the trust relationship between the two domains
- Verify the DNS servers
- Verify the time sync between the two domains
- Verify that each domain can communicate with a Global Catalog Server (GC)
- Verify that the users have the same usernames and passwords
- Verify that the users have access permissions in each domain
- Verify that the trust is in the correct direction