My Laptop can’t charge past 60%

Hello,
My laptop won’t charge past 60%. It is a Samsung ATIV Book 9 Lite laptop that I bought 6 months ago. It used to charge fully and then started getting lower and lower and now it is at 60%. I haven’t broken anything. Sometimes when I plug in the charger it takes 1 minute before it picks the charge signal. I tested the charger on another laptop and it was okay. Why can’t it charge past 60%? How do I make it pick the charge as soon as I plug in?
