Hi Phillip
Have you tried the monitor on a different PC? Is the monitor on? Reseat, verify the HDMI connection on the monitor.
If your monitor is set to auto detect or HDMI and none of the HDMI cables work, then check the connection at the back of the tower.
Your PC has the option of integrated graphics and a GTX Nvidia option. The integrated HDMI port will be disabled if you have a GTX graphics card installed in the PC.
Are you plugging the HDMI cable in the correct HDMI port?
There may be something wrong with your new PC if you are connecting the HDMI cable to the correct HDMI out port and all other variables are correct.
Grzy