|Verify the battery is correct number and is not installed upside down. |
Check that you didn't jar something loose inside. That is easy to do. Late to advise you but you need to take precautions you don't zap your hardware with a electrostatic discharge. If you have an ON/OFF switch on your power supply then leave the power cord plugged in but shut off the switch. That way you have a built-in ground. Simply touch the case to discharge any static on your body.
Re-seat all the cards, memory and cables. Only do one at a time.
Di you disconnect any wiring from the computer before opening up? You may have connected the monitor to the wrong port.
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