I had Nexus 7 authentication issues on my home network as well. It wasn't a network issue since other devices were connecting fine, and when I turned off the password I was able to connect as well. Fortunately I discovered that I was able to connect using WPS (wi-fi protected setup). I just went to Wifi Settings and hit the symbol in the top right that looks like two arrows. Then you press and hold the same button on your router and it now works.