i have a two deco setup, the first is connected to the modem and the second is in the office and they are linked via the mech technology. the main deco in the living room that is connected to the moden on the 2.5g connection is fine. the one in the office i have three computers connected to it via ethernet. 

for some reason though the 2.5g connection in th office is not working, but the other two are. when connected to the mac my wife uses on the other two connections (i think they are 1g) the network sees her and she has ethernet but on the 2.5g connection there is nothing. 

it is not the cable or the adapter to her mac and i have yet to test it with my pc, but im quite sure the issue is with the port. how do i get the port to work again? what are the troubleshooting steps i need to take?