Compaq Evo D500 Motherboard Problems

I’m a tech here at Intechra and a recent problem I been getting with the Evo’s is the motherboard is getting power but it’s turning on. Two LED’s on mobo light up with are the power and then when you press the power button or hold it, the power button light on the mobo lights up but nothing reacts to it. I’ve tried stripping it down to eliminate any hardware from causing the problems. Took out memory to at least get POST error, nothing. Any idea?