I am struggeling to get the re300 to connect to my router, c5400x. I've tried wps, either the router doesn't see the extender, or the extender is messed up. The tether app, I've been struggeling with

I just purchased this router, icannot get it to work. i can't log into it. i have it plugged into a new modem. the password on the label does not log into the roughter. igot to the web based settings