Hi,
There's a fair chance that the lamp is dead.
If the projector doesn't respond when you press any of the buttons, you need to reset the device. Do this by disconnecting the device's power cable from its power supply and waiting for at least two minutes. After two minutes, reconnect the power cable and try powering the Optoma HD20 projector on. If the projector makes a loud popping sound and then shuts off, the lamp is dead and needs to be replaced; if this happens, the projector won't power back on until the lamp is replaced.