Router connected no internet

I just bought this router today. I have registered the MAC address to my housing unit's internet network, but still unable to access the internet either through wifi or ethernet. Each time I go to the routerlogin.net page, it keeps taking me to the change admin password page. Then when I try to login to the netgear page, it gives me a message that "Serial number has already been registered".

At this point I have no idea what more to do. This was a brand new router so how can the SN already be registered?