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billblack

I could sure use some help. I have the following equipment installed on my Bertram. E120 MFD, E80 MFD, RD424 Radome, Raystar 125 GPS antenna, DSM300 and an Airmar P75 thru-hull transducer along with the original Raymarine Network Switch. Both MFDs are running v5.69 software.

We bought her as a project and installed all this gear 2 years ago (It came in the deal, uninstalled.) The configuration is exactly the same as the illustration on Page 20 in the E-Classic Series installation manual, with the single exception that the RD424 is connected to the Network Switch. It worked OK until early summer, except that I could never get the two MFDs to communicate. I had the radar and sounder on the E120 and used the E80 for GPS navigation. We put the Bertram in the dock for a few months while we worked with the treasure boat and just got back to her last week.
Presently I have nothing that will work other than the E80/GPS. The Raymarine Forum FAQs say that if the 2 MFDs won't see each other, to change the Network Switch. I did that, no change.
I reset to factory defaults/spec...no change
I have tried changing the DSM300 for another...no help. I have tried different ethernet cables...no change.
I changed out the Network Switch for a new one...no help.
When I run system diagnostics, everything checks out...Hardware, software, the SeatalkHS shows that it is active, but sees no devices.
and on and on.
I know a bit about computers and electronics, or thought I did up to now. What am I doing wrong?