First, go and make sure that everything is plugged in, on both ends of the power supply(s), both in the wall and into the computer, and try that. Don't just look, but physically check, especially in the case of the ones that attach to the computer case. You might of maybe unplugged something by accident. It's a simple check.

Next, check that you are even getting power to that wall socket, by pugging in a light or something. A circuit breaker or fuse in your house could of popped or blown. It does happen, especially if you have too many items running off of it. Just go into the circuit breaker/fuse box, trace down which circuit breaker/fuse supports that wall plug, turn it off, then back on, or in the case of the blown fuse, replace it w/the proper one. Try that. If you are running an electrical bus strip, or some kind of power surge protection, check that it is OK w/a light or something too, since they general come w/a built in resettable circuit breaker. Generally switching it off and on will reset it, via it's built in switch.

Next unplug the power supply(s) from the wall end, and leave it so for a minute or two. Then re-plug them back in, making sure the connectors are fully plugged into the wall and case, and try turning the computer on.

Finally, if you have one, use a voltage meter/multi-meter, measure for any voltage coming out of the power supply(s), to see if they are putting out any power.

If all this doesn't work, then it has to be something in the computer itself them, which may of failed.

These are simple things that I would do myself. I have had my own computer suddenly go dead one time, not the G20, but a much bigger more power hungry one, and it turned out to be a simply circuit breaker being popped out due to, too many items plugged into that circuit.

I hope one of my suggestions help and Good Luck.