No Power For Syscon Check

I recently picked up a PS3 Phat (CECHA01) with the YLOD. It has the COK-001 board. It had never been opened or serviced until now. I disassembled it and connected the UART to it to read the syscon errors. When I flip the switch on the power supply, I'm not getting any standby power (no red light on the control board). I confirmed the power supply is providing 5v to the board via the small 5 pin white cable. I also checked all the fuses (F6001, F6301, F6302, F6303, F6304) and they are good.

I currently only have the bare main board connected to the power supply via the white cable and the control board. Is anything else required to get the standby power on? All the syscon videos I've watched on YT are mixed. Some have it connected to just the white cable and other have it partially reassembled.