Symantec Endpoint Protection Manager replication fails between managers using SQL databases with the error:

[SQL Server Native Client <version>]SQL Server Network Interfaces: Error Locating Server/Instance Specified [xFFFFFFFF]. Error = [Microsoft][SQL Server Native Client 10.0]SQL Server Network Interfaces: Error Locating Server/Instance Specified [xFFFFFFFF]. 
SQLState = 08001, NativeError = -1
Error = [Microsoft][SQL Server Native Client 10.0]A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections. For more information see SQL Server Books Online.
SQLState = S1T00, NativeError = 0
Error = [Microsoft][SQL Server Native Client 10.0]Login timeout expired

This issue is resolved in newer builds of Symantec Endpoint Protection, update to the latest release version for issue resolution.

There are also these solutions available:

1. Ensure the SQL versions are up to date.
   https://social.msdn.microsoft.com/Forums/sqlserver/en-US/daa86ac4-d759-44d3-a12f-4b580ab02a0b/sql-server-alias-configuration?forum=sqldatabaseengine
    
2. Ensure the instance name was specified correctly in the Management Server Configuration Wizard.
    
3. Define an alias for BCP to connect correctly to the instance on the cluster.
   Using the TCP/IP protocol, define an alias Using SERVER\INSTANCE for the alias and just the server name in the connection parameters.
   Don't use the dynamic port, specify the correct port for the designated instance.
   See http://blogs.technet.com/b/meamcs/archive/2013/01/22/creating-a-sql-server-alias-using-the-sql-server-client-network-utility.aspx for an example.
    
4. Enable SQL Server Browser service