Try appending config with your group, mode and cvt values, plus: hdmi_force_hotplug=1
I was having a similar issue connecting my RPI3 to an older Dell monitor through a HDMI to VGA adapter and this did the trick for me.
Try appending config with your group, mode and cvt values, plus: hotplug= 1
hdmi_force_
I was having a similar issue connecting my RPI3 to an older Dell monitor through a HDMI to VGA adapter and this did the trick for me.