Build Advice Semi-modular PSU, not getting to boot

Feb 6, 2021
So I just got my new Asus rtx3070 dual. I plug everything in, I have a modular PSU so I drag 2 PCI-E cables to the two 8pin slots. Press start button and nothing happens.

I have one 6+2 cable that is not modular since my power supply is semi-modulpr so I try different combinations of modular/non-modular outputs from PSU, nothing even gets me to BIOs.

I then reinstall my old graphics card and try booting it with the modular cables (I used the non modular before) and nothing happens.

I then suspect the modular parts of the PSU, I have another PC at my television that I loot for a new PSU (also semi-modular but only has motherboard cables as static and all else is modular).

Can't boot new GPU or old GPU this way. Now I think it's the cables, except for the fact that one of the cables did work in television PC already.

I try in television PC rtx3070 and it works.

I am not sure what can be wrong or how I can continue this testing.

Here is my specs:

Main pc
Motherboard: Msi z87-g45
PSU: XFX pro xps-850w-3xb
GPU: Gigabyte windforce gtx770
PCU: i5
Storage: 2x Samsung SSD, one 250gb one 1000gb.

Television PC
Motherboard: Asus P8H67-M PRO/CG8350/DP_MB
PSU: Corsair CX750M
CPU: i5
Storage: Samsung 1000gb ssd.
GPU (not used here troubleshooting): Radeon sapphire dual-X something
Feb 6, 2021
Thanks :D

It has text that is green on the labels. So CX and M is in green text.

Probably old, at least 7 years, Corsair is probably 9 plus.