PC won't boot with new PSU

[Hammahness]

Two months ago I upgraded my gpu to a 2080 ti and my PSU has shown signs of being faulty recently. When I play games that stress my gpu and make it have massive power draw my PC has random boots. I play in 1440p so most games doesn't max out it's usage. Overclocking my cpu and ram has also caused random reboots and my only option is to leave everything at stock to not crash my PC even if it does bottleneck my gpu.

What I currently have is a EVGA 850 GQ and I was going to replace it with the EVGA 850 P2. I replaced the psu and plugged in the pre-existing cables, with the exception of the 24 pin cable, to the P2 and my PC would not turn on at all when I pressed the power button. Checked all the cables in the PC and on the PSU and everything looked good but no boot. I know there was power running through the computer because with the new PSU, lights were coming from my USB headphones which happens when the power supply is switched to on. I then put back my old power supply and It booted on normally which was weird. I thought the new PSU was probably dead on arrival so I did the usual paperclip test. If you don't know what that is, you can watch it here https://www.youtube.com/watch?v=dyVkWznvDHQ . Anyway, when I switched the psu on, the fan did indeed spin so apparently the new PSU most likely isn't dead. If that's so, my question is why doesn't my PC boot with the new EVGA 850 P2 but still does with the old EVGA 850 GQ? Should I request a replacement from amazon? Should I try another PSU? Should I have replaced all the existing cables with the ones that came with the new PSU?

Specs:
i7 6800k @ 3.4ghz
RTX 2080 Ti
16 GB RAM @ 2133mhz
Gigabyte GA-X99-SLI
970 evo 500 GB

 

[Dark Lord of Tech]

You can't use the GQ cables with the P2 power supply , they are a different PSU platforms.

Hopefully you didn't damage any components or the power supply.

P2 needs P2 cables.

 

[Dark Lord of Tech]

GQ is made by FSP
P2 is made by Super Flower

The cables aren't interchangeable.

 

[Hammahness]

You can't use the GQ cables with the P2 power supply , they are a different PSU platforms.

Hopefully you didn't damage any components or the power supply.

P2 needs P2 cables.

you sir have saved me so much time. I thank you for all your efforts to help everyone on this site. I hope Jesus blesses you with something good. Have a great new year!

 

[Dark Lord of Tech]

You have a great new year too. Glad to assist.

 

[Hammahness]

You have a great new year too. Glad to assist.

Btw, if you don't mind me asking, why aren't the cables interchangeable between the two if both are EVGA PSUs? Do those 2 companies make their power supplies differently?

 

[Dark Lord of Tech]

Yes they are different , totally different platforms and designs. The cables aren't the same.
GQ is FSP made and P2 is Super Flower made.

EVGA G2/G3/P2/T2 are all Super Flower models and share the same type of modular cables.

Unfortunately the FSP made GQ is a DIFFERENT DESIGN AND SPEC so the cables aren't interchangeable.

P2 is a great PSU , I have the 1000w P2.