Ok guys I had this issue happened on my board when I enabled secure boot without know my gpu isn't compatible with it. Now when I go to clear the cmos with the jumper pins my keyboard and mouse come back on but my monitor doesn't display anything. I have tried dvi and hdmi cable and even intergrated as well. You guys have any ideas or insight?
While trying to get rid of the secure boot watermark, I installed the default secure keys, only to then get the same problem as you - blank screen, no POST, nothing. The only way I could get my PC to boot again was as follows:
1) Disconnect PC from AC power, and remove the CMOS battery AND PCI-E graphics card.
2) Reinsert CMOS battery after a couple of minutes, but not graphics card.
3) Connect monitor cable to the integrated DVI (or VGA) port, then power up the PC.
4) It will boot into BIOS and ask whether to load defaults or enter BIOS. Choose the latter.
5) In BIOS, disable secure boot and save settings. Don't change any other BIOS settings yet though, otherwise it will go back to blank screen again.
6) After BIOS has saved and rebooted, you can power off PC and reinsert your graphics card.
7) Power PC on again and enter BIOS to set up remaining configuration options as required.
I know it seems a long-winded procedure, but this is what works for me. I've done it several times now while playing around with the secure boot stuff.