I was a macbook peasant until I decided to make the large leap to a pc,
I've got a i7-4790 and a gtx 970 (galax) with the motherboard being and B85M-G.
However the HDMI port is not working on the 970 and every time i boot up with the gpu installed there would be no signal for the monitor, which pisses me off to great lengths.
It works fine with my graphics card not installed and using the onboard graphics but for some reason when I install the graphics card it just wont work.
I don't know anything about this but I'll give you my two cents if only for a bump.
You should probably check sites for compatibility for your specs since there could possibly be compatibility issues hindering your progress.
You may also want to photograph your build and your parts and definitely at least supply links to the specifications of the parts so that readers can easily give an in-depth analysis of the issue and find a solution for you much easier.
Good luck in your endeavors.
I haven't heard of this issue before so dont quote me on this.
The cable you are using is not working properly.
The HDMI port on the GPU or monitor simply doesn't work.
Try getting a Displayport to HDMI adapter and see if it works.
Try connecting the MacBook to the display and see if it works.
The HDMI on my monitor does weird things when it isn't seated properly. Knocking on my table makes the screen go red etc, so check if you have the same problem.
If the problem still consists try talking to GALAX or write to the OEM of your monitor. They might know what is up.