All-in-one desktop will not boot up. An indicator light shows that the power supply is connecting to the computer, but the screen remains black once powered up. The only indication of a change, when pressing the power button, is three long beeps followed by four short beeps.
All devices/power have been disconnected from the computer and the power button was pressed for fifteen seconds. The computer sat for one hour. I reconnected the power supply and the issue remained.