Ensure the24-pin ATX and8/4-pin CPU power connectors are firmly plugged into the motherboard. If your CPU has onboard video, remove the discrete GPU and display from the motherboard's video outputs to rule out GPU issues.
ASUS PRIME B360M-C/CSM LGA1151 DDR4 Intel B360 Chipset mATX Motherboard w/ IO
ASUS PRIME Z270-A SERIES LGA1151 Intel MoBo WITH I/O SHIELD FREE SHIPPING ????
ASUS PRIME H310M-A R2.0 Micro ATX LGA1151 DDR4 Motherboard With I/O Plate
ASUS PRIME Z270-A LGA1151 Intel Motherboard w/ IO Shield | Fast Ship, US Seller!
ASUS PRIME B250M-C mATX Motherboard LGA1151 6TH/7TH GEN CPU DDR4 w/IO- Tested
ASUS Prime Z390-P LGA1151 Intel Motherboard | Brand New, Fast Ship!