Jackson,
I'm assuming that you mean your power supply has one of those connectors with the sliding for pin section on the main 20 pin connector. You have to plug that part into the 4 pin socket on the motherboard. I've forgotten to plug it in when switching my PS before, and it behaved in the same manner (power to drives and fans, but no post.) Pg. 19 of the manual has a small snippet of info on it.
I'm assuming that you mean your power supply has one of those connectors with the sliding for pin section on the main 20 pin connector. You have to plug that part into the 4 pin socket on the motherboard. I've forgotten to plug it in when switching my PS before, and it behaved in the same manner (power to drives and fans, but no post.) Pg. 19 of the manual has a small snippet of info on it.