The latest version of the SQL Server Native Client is "Microsoft SQL Server Native Client 2012". Please note that Microsoft SQL Server Native Client 2012 will work with both SQL Server 2014 and SQL Server 2016 as there is no SQL Server Native Client 2014 or 2016. "Microsoft SQL Server Native Client 2012" can be found in the Feature Pack for SQL Server 2012 which is located at:
The specific file you are looking for is "sqlncli.msi" Please note there is a 64-bit version and a 32-bit version.
Download the one that matches the Operating System's architecture and install it on every Service Desk Manager server.
After installation verify the issue is resolved by running "sql_check_db -c" again. It should now be successful.