Okay, I was having the same problem not able to connect via LAN but able to connect via wireless, and DHCP was assigned to wLAN. Weird.

Anyway, in case anyone else had this same problem I solved this by selecting Dynamic PPPoE instead of Static. (eventhough we have static).

TM Support will advise you to use Static PPPoE. Use Dynamic PPPoE. You will still be using your assigned static IP when you connected.

Just to expand, this are the things you don't have to do from the discussion here:

DON"T DO THESE
1) U should port forward the external IP to your internal server IP.
2) First, configure your server network card's TCP/IP stack to use a static RFC1918 IP address that is outside your DHCPv4 IP pool. Then click the 'Advanced' button, go to 'IP settings' tab, and then add the static IP provided to you there (gibberish, no need to do this)

3) With that setting above, in the server's network interface, try manually putting aaa.bbb.ccc.42 as its address, gateway being aaa.bbb.ccc.41 and netmask 255.255.255.252. Then in the 'IP settings' tab, add a static RFC1918 IP address there (192.168.0.201) and a gateway that is 192.168.0.1. (even crazy.. what?! No, don't do this)

The solution is:
1) Then the only other thing to do is to set the PPPoE to dynamic mode, then manually assign the static IP to the server's network interface and then add a static route too there. (YUP, JUST DO THIS)

Hope this helps someone!