You need to check the adaptor first
check voltage at the jack plug - centre to outer pins should be as written as output on the adaptor typically 19v DC on modern laptops. This proves output from adaptor is OK
next check the DC jack socket in the laptop is not loose or centre pin broken. these sockets are a common failure point whn they lose their connection to the motherboard.
after that its more serious as power board / motherboard in laptop could be dead.