I'm trying to replace my power supply and I've been trying to get the 24-pin connector out, I've been pushing down the retention clip really hard but still no progress, is there something I'm doing wrong?
They can really get stuck! You might want to get a very small screwdriver and gently wedge it under the clip so you can use a bit more force to pull up on the harness/connector. My Thermaltake PS connector and Asus MB were so tight I comically fell over backwards when it finally came out! Of course, it then came in and out easily. Your probably doing nothing wrong!