Openplotter to WiFi multiplexer on Pi4

[UserError]

Hello, I have spent an inordinate amount of time not getting anywhere with this.
I gather it's a good idea to connect external devices to SignalK, then connect OpenCpn to that.
I have a little VelaNavega NMEA2WIFI multiplexer. ATM, I have a Garmin GPS 152 connected to it. The LEDs in the multiplexer flash when the GPS is on, so I presume it's getting data.
I've entered what I thought was the right info into the SignalK connections page and in Opencpn. However, I'm not getting anything through.
I would be grateful if someone could advise how I get SignalK connected to the multiplexer, and then pass that data to Opencpn.
I have read n+1 amounts of documentation and watched many videos - none of it seems to (me) to tell me what I need, but I will freely admit to not being well up on networking and all the serial/usb alchemy that goes on. I'm also at anchor, with limited internet.
Many thanks.

[HeywoodJ]

This is going to be a little hard to diagnose without a little more detail.

Do you have a reason to use SignalK? It is great if you want to use the data for more than OpenCPN, but if your use is just to get the data into OpenCPN then probably much easier to cut out the middleman and go direct.

Is your OpenCPN computer connected to the Navega WiFi network? Can you open the Navega webpage? That is the first step. If you are connected, and you haven't changed anything, then in OpenCPN set up a new "network" connection. Select "UDP", Address = 192.168.4.1 and Port = 2000 (or whatever is shown on the Navega webpage).

If you get that working, and you want SignalK instead, then you can move the connection to SignalK.

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