Can't access router after flashing with DD-WRT

I just purchased a Netgear Nighthawk R7000.  I read up on the process and flashed it with the.dd-wrt.K3 R7000 chk file from Nov. 2017.  I reset to factory default but I can't get into the interface of the router.  I put in the 192.168.1.1 into the webpage but it comes back there is no internet connection.  I can turn on the wireless and can see the wireless network named DD-WRT but when I try to connect it asks for a security key.  I have tried a reset again but the same thing keeps happening.  I would appreciate any help that can be given on either to access it or reset it back to the Netgear factory default.  Thank yoiu.