RESOLUTION:
1. Verify that you can access the LDAP using Softerra LDAP Browser
2. Verify that you selected the correct OUs in source/target in the CMN/DC connector.
3. Verify that the migration account has enough Domino permissions.
4. Enable LDAP Debugging on the Domino Console to trace the LDAP conversations
see article:
https://support.quest.com/coexistence-manager-for-notes/kb/188045
5. Check the setting for the LDAP timeout from Domino Admin (server configuration).
if needed, increase it or reset it to "0" (unlimited).