Question Newly buid PC starts but has black screen

[tacheg]

Hello,

I've just assembled new PC. All parts are brandly new. When computer starst all fans are running, graphic card is blinking colours (RGB fusion) but nothing happens, screen is black.
X570 Aorus Elite
RTX3080
5900X
PSU 850W

What I have tried

1. Rebuild it onc eagain
2. Run with only one RAM card
3. Tried all graphic card ports
4. Changed PSU cables

A am little bit desperated. Tried alot of options, and nothing works :/

 

[rgd1101]

update the bios?
what the make and model of the 850w psu?

 

[tacheg]

I am trying to update bios using Q-flash plus, but nothing happend. Try it again
PSU: SeaSonic Focus Plus Platinum 850W