To troubleshoot a cross-domain authentication issues, the following steps may need to be taken:

1. Verify the trust relationship between the two domains
2. Verify the DNS servers
3. Verify the time sync between the two domains
4. Verify that each domain can communicate with a Global Catalog Server (GC)
5. Verify that the users have the same usernames and passwords
6. Verify that the users have access permissions in each domain
7. Verify that the trust is in the correct direction