Perhaps another issue with Mac OS 10.11 El Capitan.
Using the current Actual Driver package, installed after the MacOS 10.11, a connection to the Server running FMS 18.104.22.1684 will never succeed.
Error returned is
[FileMaker][FileMaker] Failed to connect to listener (2)
(P.S. same configuration of drivers and connection, in same network, works perfectly well with MacOS 10.10 Yosemite)
Perhaps tsplatypus can have a look; the other ODBC issue with 10.11. of December 2015 is still not solved either