Take a screwdriver or paperclip and touch (short across for an instant only) those two pins that say Pwr Sw (on the front panel header) and see if the rig comes on. It should be plugged in and all hooked up to work and should come on.

If it comes on by shorting across it, but not when you push down the off/on button with it connected to those two pins, then you have a bad off/on switch. If it doesn't come on, you have another issue with power someplace.