When I push button to turn on, the light flashes orange. Nothing happens, no fan, nothing. It worked fine yesterday.

It cannot be imagined what exactly may be the issue with your system. Still you can follow instructions on this service manual for this model.

It will be more helpful if you provide the details of Diagnostic LEDs on your system. Diagnostic LEDs are 4 LED numbered as 1 2 3 4 and indicate the kind of error as per their on of sequence.

Good day sir/maam, the reason why its flashing orange is that there is no stable power, this could be caused by the following, so check each one out.

1. Bad power supply, to test if your power supply, remove the 20 or 24 pin molex connector to your motherboard, locate the green wire, get a piece of wire about 4 inches and short the green wire with the black wire (any black wire) plug in your computer, you should see the fan spin. if not replace your power supply. If the power supply fan spins, remove the jumper wire, unplug your pc, reconnect the molex 20/24 pin on the motherboard. (check you mains if 110v or 220v, if its 220v plug on a 110v would yield the same symptoms as you described).
2. Bad memory module, the memory modules are the thin flat boards near the processor, remove the memory module by releasing the side clamp, clean its contact plate with an eraser. then replace it. Test again. do it several times.
3. (optional, if applicable) Bad video/graphics card, you may hear 1 long and 3 short beep. if this happens replace your graphics card.

This usually means a failed power supply and/or failed system board. No way to know further without swapping parts. Power supply is cheaper to replace .