so when it's connected to the router it doesn't work, but when the connection is on your desktop it works?
i think it is because you always had the internet on you're desktop pc, so that Mac adress of the network card, is registered by your ISP.
the thing that you can do, is clone you're mac adress, of you're desktop pc, in to you're router.
When you're logged in to your router, you can find it under the tab "MAC Adress Clone"
So that you're ISP thinks that you're desktop pc is connected, then you will get an IP adress from your ISP.
Then It's got 2 work...
Did for me , and many other people