Hi,
Perform a hard reset first PC might be in a hibernate mode. Remove the battery and AC adapter then press and hold the power button for around 20 secs. Put everything back together then turn it back on. If there's still no display but there's light on the laptop try hooking up an external monitor and check if you'll see any display on it. Lastly re-seat the RAM, remove the battery, charger and RAM and put everything back together after couple of seconds.