The main reasons behind your Asus laptop not booting up are,
It has a bad power adapter
It has a bad battery
It has a bad screen
1. Bad adapter: When the adapter of your Asus laptop is not working properly, then the laptop would be able to function with the battery of your laptop. In case the battery drains out completely you would not be able to turn on the computer. Check whether the adapter is faulty by getting someone else’s adapter and try charging the battery. If the battery gets charged then the fault is with the adapter. Replace the adapter with a new one.
2. Bad battery: The laptop would run only if the battery is plugged into the power outlet. In case the laptop is unplugged from the power source then the laptop would turn off and would not turn on. In this case, the battery has to be replaced.
3. Bad screen: Maybe the screen of your laptop has become bad. Check this by plugging in the power adapter to the wall outlet. And when both your battery and adapter is working properly then the problem might be with the screen when your laptop is not turning on. You might have to replace the screen.