That is strange for it to not work. Can I just confirm that you are still getting flashes from the AIS LED? If so then there is an issue with the connection to the chart plotters.
On the Simrad NSS3; please make sure that the ‘NMEA OUT’ cable is connected to cable 4 and 5 of the NMEA 0183 on the Simrad NSS3. I couldn’t say about the other chart plotter.
If you are worried that the unit isn’t working then please try the WiFi on your mobile phone or PC. Try it with the OpenCPN APP or easyAIS. This will show you what it is receiving. We are confident that it is working, as you mentioned seeing the LED flash. Please try the connections again and with WiFi on mobile. Please let me know
Best regards