upgraded GPU from RTX 2060Super to RTX 3070 and now system wont boot

Hello Everyone,

Im hoping this is ok to post here..I didnt see anything against it in the sidebar.

I need some help troubleshooting an issue im seeing with a GPU upgrade.

The system specs are here: https://pcpartpicker.com/list/2KQHgB

Basically, when the 3070 is installed, using a single PCIe cable with 2x 8 pin connectors from the PSU to the GPU, once I try to apply power, the lights in my system (and the card) flicker for a quick second, then stay off...The RAM RGB lights stay on but thats it.

I moved the RTX3070 to my 2nd PC (older):
Asus Z97-E/USB3.1 ATX motherboard
i7-4790k CPU
CX750M PSU

The RTX3070 shows the exact same behavior. System lights flicker quickly then never come back on and system does not boot..

I am currently in the process of setting up my 5600X system with a BIOS update. But other than that im not sure what more I can do. Any advice?