Recently got a laptop with Core i3-5005U Intel HD Graphics 5500, the HDMI is not working under Windows 8.1 x64, with latest driver. Also did a clean install of Windows 8.1 then install the latest Intel Driver only, no other software, still not working. The HDMI cable is high quality, works on my i7 4790K desktop (both Intel HD 4600 and Nvidia GTX 970 HDMI), and another 3rd gen i5 laptop. I first suspect a defective HDMI port, but then I suspect Intel Driver wasn't optimized for the newest gen Intel Graphics, so I tested with Ubuntu 14 Live OS, and later install actual Ubuntu 14. The HDMI port is working under Ubuntu out of the box, no driver is needed to install.
So is Intel going to fix the driver? Or is this hardware defect? Under Windows 8.1 the screen of the laptop will blink and make a connect sound then disconnects, it actually detects the monitor for 1 second. The monitor's signal light also came up for 1 second (but no display)... Under Ubuntu there's no such issue. I built my desktops and repaired a lot of laptops, but this kind of issue is new. Looking for Intel Forum Moderator to file a ticket about their driver problems..