I guess you are saying you have a backlit KBD and the backlight is on.
You need to look at the status LEDs and post what they are doing.
If they indicate the LT is booting up, then you have a display problem.
You can do a flashlight test on the display.
If it is not booting up then there are lots of other possibilities, including an HDD/SSD issue, RAM, CPU, or other MB problem.
If you can't define more symptoms, then take it to a repair shop.