Perform a factory reset on the 615 and then connect 1 wired PC to the back of the 615 using the LAN ports.
Use a web browser and input 192.168.0.1 and the routers web page will or should be displayed. Log in is Admin and password is blank so just select the log in button. There is a on board set up wizard that you can run from there.
CABLE or DSL and what is the make and model # of the ISP modem?