Hi there,
Same problem by my side, have you got a way to make it work or just had to replace it?
I got the Ethernet switch from an official EU dealer, I power it from the ROV, power light gets on bright green but no activity light when connecting the fathom, DVL and navigator, tryed with and standard network switch and all when online and worked so cables and devices are ok and their ip addresses are ok
Have you any clue how i can make it work? or how to diagnose if it is faulty ?