If the HDMI cord plugs in monitor and HDMI port then I call it connected. But it appears that your first built by you PC is defective in some way. Given only this no one might guess what is faulty.
The usual next step is to make it very very small. You don't need drives, more than one stick of RAM and no case. If the least number of parts to get a display fails, then what is left has an issue.
So i built my first PC after saving up for 3 years and my PC wont connect to my new monitor. I'm using HDMI and I have already tried both the MoBo and GPU. My monitor isn't asleep and my HDMI cord works for my Xbox so i know its not broken. I need help please