When posting a thread of troubleshooting nature, it's customary to include your full system's specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
OS:
Have you gone through the how to build guide linked below? Perhaps you missed plugging on of the connectors, like the 4/8pin EPS connector? Have you made sure you've installed the processor in the right way without any bent or broken pins on the motherboard CPU socket?