Power on and screen off

This laptop has Lenovo LCD test - at least to verify screen is working: Fn + left Ctrl + Power, should cycle through 5 colours for ~20 seconds.

If screen is working:

try: unplug power and any USB devices, then hold the power button in for 30 seconds. (It should turn off completely)

try and turn it on - ?

If still the same, open it up, disconnect the main battery and try again.

If still no go, find the coin-cell battery and unplug its 2-wire lead from the board, then try again.

Let us know how you go.