On an HP ProBook 6470b with Intel HD 4000 graphics, adding the following line to /usr/share/X11/xorg.conf.d/20-intel.conf resolved this issue in addition to fixing the resolution of my external monitor at the login screen:
Option "ReprobeOutputs" "true"
On an HP ProBook 6470b with Intel HD 4000 graphics, adding the following line to /usr/share/ X11/xorg. conf.d/ 20-intel. conf resolved this issue in addition to fixing the resolution of my external monitor at the login screen:
Option "ReprobeOutputs" "true"