PC shows no life at all.

I've replaced the GPU, MOBO, RAM in my friends old pc, but for whatever reason between transit it seems something just died in the computer. Nothing turns on, no fans even begin to spin. No light on the motherboard. Worried that somehow I broke the new motherboard, and I'm becoming overly anxious about that possibility.

The motherboard has no signs of life, and it never did since I plugged it in so I'm guessing it's probably the PSU, but I can feel the current when I've bypassed the power button. Just hoping I didn't somehow fry it because the psu wasn't working.

I'm just confused and wondering if there's anyway I can test to see what might be wrong, but it feels like without even a single light or bit of power to the pc my only option is hope a new PSU works or continue to replace every single part until I've built 3 pcs lol