Advent T100 All in one system

Question

I have Advent T100. It does not boot up all that happens is the hard drive spins I have checked the power and it always has 12v supply to the motherboard. A few times the fans have spun for about 5 seconds, if this hapens when they lose power so does the hard drive but the motherboard still has 12v power to it and through the cable to the motherboard plug. Is the motherboard at fault?