Help - Humminbird Ethernet Hub issue

[Eornom21]

I just added to Solix 15s and an Ulterra to my boat. To network all three, I added a 5 port Humminbird ethernet Hub. But when I go to configure Network on either Unit, they don't see each other. And neither is finding the Ulterra. I had someone check the voltage of the power supply to the hub and it was apparently ok. I switched out the ethernet Hub for a new one... same problem. I factory reset both graphs. No help.

I'm stumped... any ideas?