[HELP] How do I enable DIAG port to Unlock the LG G3 Vigor (D725) AT&T?


I am trying to unlock the LG G3 Vigor (D725) for AT&T. It is on Lollipop firmware and then message pops up telling me to type in 277634#*# or 3845#*#. These codes do not work at all for me.

How can I unlock this phone? How do I enable DIAG mode? Can anyone help please? Thanks!