es128 setup doesn't see ST-60 Instruments

I've just finished the installation of a new es128 MFD on my sailboat. I want it to display data from an ST-60+ Tridata and an ST-60 wind machine. The two older Sea Talk instruments are connected to a ST to STng converter and that is connected to the MFD. When I attempt to set the data selection on the MFD I get the following error message: "The following devices are preventing data source selection E22158-Sea Talk STNG converter S/N:0651037. Please see user manual for details."
What does this mean and should I do?

Thanks,

Steve