External monitor with HDMI VGA Adapter not detected - Ubuntu 17.04

Solution 1:

-- EDIT ---

I just realized I posted this without seeing that you already tried most of these steps. Leaving it up here in case it's useful to anyone. - Matt

Having been through this recently with a new monitor, I can relate to the frustation of this.

Though I can't offer a solution, I can suggest steps to diagnose.

Diagnosis steps to try:

1. check Ubuntu displays settings. (main menu -> settings -> displays)

See if your monitor is recognized there.

2. Check monitor is recognized by xrandr: First You can check to see if your monitor is detected at all using these commands:

   xrandr -q --verbose

You'll get some output that looks something like this:

Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1920x1080+1920+0 (normal left inverted right x axis y axis) 293mm x 165mm

1920x1080     60.00 +  59.93* 
1680x1050     59.95    59.88  
1600x1024     60.17  
1400x1050     59.98  
1280x1024     60.02  
1440x900      59.89  
[...]

Somewhere in there, you should see an HDMI connected section:

HDMI-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080     60.00*+  59.94  
1680x1050     59.88  
1280x1024     60.02  

If not, there's probably a cable connection problem

3. See if your monitor can be detected connected to another non-ubuntu machine using the cable adapters you have. If it's recognized there, you know your adapters are not the problem.

4. Check your video card type: lspci | grep VGA

   I found several forum posts suggesting that there is some kind of problem with Nvidia drivers, and sometimes your system is not getting correct resolution information for your particular monitor. The solution there seems to have to do with updating the Nvidia graphics drivers.

Solution 2:

My solution,

Plug the adaptor in alone. Then plug the vga cable into the adaptor.