Toshiba laptop does not work after a long time?

My Toshiba Satellite c55-c-1lv does not start up; I've had the problem for years that it's getting slower (that's why I used it less), a few months ago it took me longer to recognize my mouse. And a few days ago I wanted to start it and delete all the old data to reset it, but the power button did not respond; the light in front continues to glow orange when I plug in the power adapter.

I do not know what to do.

Maybe the battery is dead and the power supply does not provide enough voltage or can't hold when the laptop draws power to start. Another NT available to try out?

How is your laptop not started? Is the picture displayed or is the screen itself completely black?

The laptop does not start completely, neither the power button lights up nor the screen react.

OK, then it's because of battery. Try to wait while charging, and try again later laptop turn on. If that still does not work within 6 hours, then you need to buy new battery.

I read that you unplug the battery and the power adapter, press the power button and then both should do it again.

Yes then try it out.

Unfortunately, it still does not matter, could it be because I have not used it for months?

Can be, because even if you do not do anything with battery, it is still weaker, and if it is completely discharged, then you can't recharge and you can dispose of this battery already and buy new.