My system had been working happily for years then about 3 weeks ago it crashed. After reset it would allow only one device to access the others required a password. Each tim ethe router pwd was added it came up as authentication error.

I bought a new kit but the same issue continued . 

I then contacted my broadband supplier BT in the UK  . They sent out a new hub which I tried today  but I am still having the same authentication issue after the first device . Any ideas?