1. Re this
I recently bought a new pc in pieces
does this mean that you bought the parts separately - all being new and then assembled them
OR does it mean you bought some manner of disassembled computer - on special offer - advertised as new but not working and sold on offer.
The reason I ask is that, whilst appreciating that English is perhaps not your first language, the wording
I recently bought a new pc in pieces
is a little unusual for what is often said as
"I have just built a computer using the following parts etc."
2. If you could answer the questions asked it may make it easier to help you
I appreciate a number of people have replied to you but you do not answer what is asked
By that I mean
What monitor and what type of video cable are you using to connect to the computer?
asked in post 4 and never answered.
3. The RGB leds on the board being lit have no direct relevance to it booting - those will light if power is supplied to them
4. Often the cause can be the wrong connection to the 8 pin CPU power on the board. If a PCIe power connection (graphic card power) is used there instead of the CPU it will NOT boot
5. That CPU was configured by BIOS for use on this board on BIOS version 0408
Core i7-8700K (3.7GHz, 6C, 95W, L3:12M,HT) ALL 0408
I doubt it is a BIOS problem as the CPU was released April 2017 and the BIOS on release of the board was version 0407 on 8 Sept 2017
6. If you get no further checking All CONNECTIONS CAREFULLY, I would recommend the connection of a motherboard speaker and check any beep codes
Speaker connection page 1-17 of motherboard manual