My PSU is shutting off when I try plugging a second SSD power cable into it, how do I fix this?

Currently trying to add a second SSD to my PC setup, I have an SSD to PSU cable I ordered online that is specifically meant for my PSU, but when I try to plug it in my PSU shuts off immidiatley. Is there a part I need to replace? Something I'm doing wrong? SOS

Specs:

* MOBO: ROG STRIX B450-F Gaming

* PSU: Powerspec bronze 750w PS750BSM

* CPU: AMD Ryzen 5 3600 6-core