Wild guess, but did you maybe disable it?
Settings -> wireless & networks -> more -> NFC, Android Beam
And I think bluetooth also needs to be on.
NFC on the Nexus 7 is positioned just where the logo is and a bit above it on the back side.
Nokia Lumia 925 16GB
Nexus 7 32GB, 4.4.2 stock, rooted, Xposed installed
Sony Ericsson Arc S, 4.0 .587, rooted
Dropbox for you: http://db.tt/Qk80xRg
500MB extra for both of us.