Question System not booting with GPU installed ?

[aaaaakljdshflkjashdflkjsa]

Motherboard: Biostar BTC 360 D+
GPU: 2 x Radeon VII
CPU: Intel Pentium Gold G5400(has igpu)
PSU: Corsair RM1000X
SSD: kingston 120 gb ssd
RAM: PNY 8 gb 2400 mhz

So basically when power on the system without the GPU in one of the 7 working slots, it works fine, I can access Windows 10 and the BIOS.
But when I plug in either GPU, it doesn't boot at all, all i can see is the black screen ?
The PSU is also working because I have tested it.

 

[Lutfij]

Welcome to the forums, newcomer!

How old is the PSU used in the mining build listed above? Mind sharing how you tested the PSU? Which BISO version are you on for your motherboard?

 

[aaaaakljdshflkjashdflkjsa]

Welcome to the forums, newcomer!

How old is the PSU used in the mining build listed above? Mind sharing how you tested the PSU? Which BISO version are you on for your motherboard?

thank you!

The PSU is brand new, and I made a bit of a mistake in the original post, I meant powering up, the whole system isn't powering up.
I tested this PSU by using a tiny cheap case fan that I have lying around by connecting it and by putting a jumper cable, in the green wire (in what is supposed to be the motherboard PSU, but isn't because this board uses 8 six-pin connectors to power the board ).
And as for the question about the bios... i don't know, (this is my first build)
hope it helps!
EDIT: just checked bios number its B36CF505.BSS
Thanks for answering btw!

 

[aaaaakljdshflkjashdflkjsa]

UPDATE!
I got one of the GPUs to work!
it is recognized and functions properly!
the other one lights up and has fan spin but displays a black screen

 

[aaaaakljdshflkjashdflkjsa]

Update:
both gpus have stopped working
i might buy 3080s instead