Remove power from everything, monitor included.
Set the BIOS config jumper to pins 2-3, re-apply power to your motherboard & monitor. This boots the motherboard straight into the BIOS configuration. Check for "Fast Boot" options, and if any are enabled, set them to disabled. Save and exit the BIOS, remove power from everything again, and set the BIOS config jumper back to 1-2.
If you still receive no video output in the BIOS using the onboard HDMI connector, repeat the same steps using a PCIe graphics card if you have one handy.
I prefer using VGA connections in the BIOS since I find digital connections like HDMI flaky and slow, but I realize it's not always possible for everybody, especially these days