Hi,
It could be that you have done manual configuration for operator listings. Could you please reset your router to make sure that you haven't done anything that could prevent you from connecting?
Also, have you updated your firmware version before this happened? if you didn't - you could try doing it.
There's a slight chance that AT&T could have done something too unless you're sure that the reason for not connecting to the operator is the software/hardware of RUTX11.
EB.