razer blade 15 doesnt turn on if i didnt plug in the cable

when i bought razer blade 15 i tried to turn it on, but it doesnt turn on i guess the battery is dead so i charge it for 4 hours, but still doesnt turn on, so i try to turn it on while on charge, it works. i check the battery its 79% but it said “not charging”. knowing its 79% battery, i plug out the cable but the laptop is suddenly turn off