fibre installed devices won't connect via wired connection

[#1]

what a day, fibre installed, engineer test said i was getting 80mbs - turns out BT speed test says 20mbs, but that's the least of my worries at the moment. Both the hard wired mac G5, wired wireless booster and sky HD box will not recognise the router.
The Mac G5 hangs / freezes whilst it's looking for a network it can't find, sky box has no on demand all of this despite both working absolutely without problem on adsl for the last  few years.
Support from plus net after 2 calls was a total waste of time, none of the 'helpers' could offer any useful advice. One even resorted to googling for an answer, as I say router works fine on wifi but the devices that need to be hardwired.. absolutely nothing... any help/suggestions please

[#2]

Does anything work wired? Laptop? Have the devices you've listed previously been setup with fixed IP addresses that now may need to be changed?

[#3]

I've just been connected to fibre this afternoon and had exactly the same problem.  Everything works over WiFi but I can't connect my wired network.  I've used 2 different leads and 2 different ports.  Rebooted PC and switch to no avail.  Finally I bypassed my switch and connected directly to the plusnet 2704n and got a connection.  I am investigating further and will post an answer once I finally work what the issue is, I suspect some problem in the Plusnet router negotiating the connection

[#4]

none of the wired devices work anymore, i presume changing the IP address is straightforward, shame PN staff couldn't give me some helpful advice on the matter - thanks

[#5]

I've fixed my problem, hopefully this helps you.  When I installed the new fibre router I had unplugged the old ADSL router and plugged in the new router using all the old cables that had been working fine.  For this reason I was blaming the Plusnet unit, but when I pulled all of the cables out and tested them I found one had a single broken wire.  It looks like the Sagem unit is particularly sensitive to the cable being fully wired even though it is only a Fast Ethernet, rather than Gigabit port.  Check all your cables, and make sure you have a single known good cable between the LAN port on your router and your PC.  Once you have that working build out from there by swapping cables if you don't have an Ethernet cable tester.

[#6]

alanh2a
Try setting the IP address of the devices manually - i.e. :
IP = 192.168.1.200 (or 201, 202, 203 for consecutive devices)
Subnet = 255.255.255.0
Gateway = 192.168.1.254 (the IP for your router)
DNS = 8.8.8.8 and 208.67.222.222
You may also want to power cycle any devices that are connected to the network - sometimes conflicting IP addresses and different subnets confuddle things.

[#7]

Thanks Imillard, have tried new cables and hard wired works fine on a newer machine, DomS wu=ill try setting IP addresses manually and report back - many thanks