Hello and welcome to JustAnswer, I look forward to assisting you today. Normally for the extender, the cable is used only for initial setup; otherwise it is a wireless device used to extend the signal of your router.
Well it isn't hurting anything. You will need to set it up to work with your network. The other cable sounds like it is okay.
You may disregard the Premium Service Offer for Remote Support. That is an automated popup initiated by the web site.
That is what I am trying to tell you. That popup is automated and I cannot fix it by a remote connection to your computer.
Do you have any further questions?