Unplug the power cable from the back of the case(PSU). Push(and hold) the power on switch for about 10 seconds - to discharge capacitors. Plug power cable back in, and then try and power it up.
i have the same problem! Fans, HDD, motherboard all work but no signal to monitor and also solid orange power button.
And did you try what one of the posters suggested? Resetting the BIOS may help. If that gets you nothing, could be a power supply issue or a bad motherboard, check capacitors to make sure they are all in good shape.