Since it looks like 24 pins isn't required and you had everything hooked up right, try clearing the CMOS. What you need to do is remove the battery on the mobo. Then you need to find the CMOS jumper and move it one pin over. According to the picture, it looks like it's next to the battery, but I'm not completely sure. I would look in the manual before trying.
After you do both, wait around 30 seconds, replace the battery and move the jumper back, and report back with what happens.