My screen digitizer is not working. Model GT-N8020

My screen digitizer had some problems lately, the screen responds well to the s-pen but fails to recognize the finger touch, it started with top half of the screen in the landscape orientation not responding , now the whole screen stopped working.

but it still works with an s-pen..

But the screen magically starts working fine when connected to the charger,

can anyone please help.. thanks in advance.