It makes sense that the 64-bit DSN isn't going to work, especially with server side scripts. I think it's odd that you can't see the 32-bit DSN. Are you building (working in FMP) the connection while working on the same machine as the server? Just curious. Is that Microsoft SQL Server? What version? You might check around for version compatibility betwen FMS12 and your SQL ODBC driver version. Sorry that's not a real solution.
Here's the compatibility list: http://help.filemaker.com/app/answers/detail/a_id/6420