Why can’t I access my wifi with my new Nook?

I’ve had wifi for a year. All my gadgets work fine. Just got a new Nook. Going through the set up it’s asking for a password. I’ve tried everything. I’ve shut down the modem and logged pack on with my pc with no problem. That password won’t work on the Nook. I’ve also used the acces number off the modem. Help!