With a modded Bios on RX 470/480 and 570 cards you need to use the AMD pixel patcher to bypass the signature check or you will have a code 43 error in the Windows Device Manager and they won't work. Most RX 580's don't need the patcher. Apply the patcher after installing or updating the AMD driver and reboot. If you are still having trouble, try removing the drivers in safe mode using DDU, install the latest AMD driver, apply the pixel patcher and toggle compute mode on in AMD settings for all the cards.
https://www.monitortests.com/forum/Thread-AMD-ATI-Pixel-Clock-PatcherI just tried booting into safe mode through msconfig and now I only see a black screen and nothing else! I am connected to one of my video cards with HDMI and I can't get it out of safe mode!
It is always a good practice that you go first in the BIOS and set primary display as IFGX which means primary display will be used the onboard graphics, you can hook up anything your motherboard supports, usually VGA is there as an option. After that you start troubleshooting your rig, by installing cards one by one and modifying their BIOS (check BURIEDONE videos on YouTube).