I dont have uverse but my cable box will also connect to Netflix. I found it wasnt as quick of a connection through the cable box as from the TV app or my roku so I usually watch Netflix on roku.
I'd hard reboot the main uverse dvr box (not just the wireless receiver if that's what this is) and then log out and back in to the app and see if that works. Uverse had decent chat support back when I had them, so you may want to troubleshoot with their chat.