have you rebooted the router? you havn't really giving a lot of detail for us to help you with your problem. when you say "no device can connect to wifi" do you mean no device can see your wifi or you can see it but if you try to connect nothing happens?
if its the later do you get any error message? im not sure if xfi provides logs but i would check around in the web interface and see if you can find the logs. this will tell you excatly what is going on.
also are you able to use your internet hardwired?