display - My Linux desktop sees my HDMI-connected monitor, but my monitor says "No signal"

I have a Gigabyte H55M-UD2H motherboard and an Acer S271HL monitor. When I connect the monitor to the motherboard via VGA, signal works perfectly. When I connect the monitor via HDMI, the system "sees" the connection, but the monitor receives no signal (the monitor shows a blue box which reads "No Signal" and then the monitor goes into power-saving state).

Some fun facts about this:

• if I hook a different monitor to this box via HDMI, the monitor receives the output without issue (same computer/motherboard, same cable, different monitor)
• if I connect a different computer to the monitor via HDMI, the monitor receives the output without issue (different computer, same cable, same monitor)
• no signal is received whether in the OS or in the BIOS
• there are no BIOS options for controlling video output other than for selection of onboard vs. PCI/PCI-E-based video card (the system has no dedicated video card installed)

The box is running Linux, so I have the output of xrandr which shows the connection and the monitor modes detected via DDC:

~$ xrandr --prop
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          
DP1 disconnected (normal left inverted right x axis y axis)
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          
HDMI2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
    EDID:
        00ffffffffffff000472ca028d128022
        1c160103803c2278ca7b45a4554aa227
        0b5054bfef80714f8140818081c08100
        9500b300d1c0023a801871382d40582c
        450056502100001e000000fd00384c1f
        5311000a202020202020000000fc0053
        323731484c0a202020202020000000ff
        004c55573044303130383531300a01e5
        020324f14f0102030405060790111213
        1415161f230907078301000067030c00
        1000382d023a801871382d40582c4500
        56502100001f011d8018711c1620582c
        250056502100009f011d007251d01e20
        6e28550056502100001e8c0ad08a20e0
        2d10103e960056502100001800000000
        000000000000000000000000000000de
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          
   1920x1080      60.0*+   50.0     25.0     30.0  
   1680x1050      59.9  
   1680x945       60.0  
   1400x1050      74.9     59.9  
   1600x900       60.0  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1280x960       60.0  
   1366x768       60.0  
   1360x768       60.0  
   1280x800       74.9     59.9  
   1152x864       75.0  
   1280x768       74.9     60.0  
   1280x720       50.0     60.0  
   1440x576       25.0  
   1024x768       75.1     70.1     60.0  
   1440x480       30.0  
   1024x576       60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   720x576        50.0  
   848x480        60.0  
   720x480        59.9  
   640x480        72.8     75.0     66.7     60.0     59.9  
   720x400        70.1  
HDMI3 disconnected (normal left inverted right x axis y axis)
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          
DP2 disconnected (normal left inverted right x axis y axis)
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          
DP3 disconnected (normal left inverted right x axis y axis)
    Broadcast RGB:  Full
        supported: Full         Limited 16:2
    audio:  auto
        supported: force-dvi    off          auto         on          

How do I get this monitor to recognize the output from this HDMI socket?

Have you tried actively changing the display? One of the following should work for you:

1. gnome-control-center display (if you are running gnome or cinnamon)
2. disper you may need to install it first
3. xrandr --output HDMI2 --auto

Mind you, I'm not sure how you can run these commands with no screen attached. Should work if you can connect a VGA screen and then activate the HDMI. You could then add the command to a startup script (assuming it works) and, at least, have output when you're in the OS.

Apprently, this was fixed in Ubuntu 13.04. I'm not sure what specifically was updated to fix this, but my guess is that it was something with the driver. What's weird is that it also fixed it for the BIOS. In any case, this isn't really a "answer" as I don't know exactly what the problem is, but as usual, "upgrade it" is the solution.