During cv19 I ran a computer retailer warehouse. We were a SI but also sold components, pretty standard storefront for that industry.
One of our customers did just this, purchased a new PSU to pair with their prized Aorus Master 3080. Didn't swap a single connector, just plugged it all in and hit power. No POST, just nothing...
Most components failed tests on our testbench, was a big rip moment for that customer. We waived the diagnosis fees and quoted them on a new system subbing' in components from their cooked build.