Seting up A 2nd router behind an AT&T 2Wire UVerse Router

I have a netgear n600 wireless router that has been working fine right up until I had attuverse installed yesterday. The installer said I would be better off keeping the n600 rather than the att wireless in their router because it has a better range. I don't know what he did, but everything works except the wireless router. It is connected to the att router the same as our mac and pc, but is NOT putting out a wifi signal. Any ideas? (I am waiting on the installer to return to see if he knows what is wrong.)