Use a Voltmeter to check that there is 19.5V DC on the output plug of the charger to prove that is supplying the power to the laptop.
If the charger is OK then you need to open the laptop and check that the DC-In jack is OK and that there is continuity through the jack to the motherboard. Sometimes the centre pin of the connector breaks internally. They cannot be repaired, they have to be replaced.
Here’s the maintenance and service guide for the laptop, taken from this webpage. Go to p.89 to view the necessary pre-requisite steps and then the procedure to remove the power connector cable.
You initially don’t have to remove it, just disconnect the power connector cable plug from the motherboard and then use an Ohmmeter to test the wires for continuity between the jack and the cable plug.
If the jack is faulty, the spare part number is 719859-001. Search online using the part number only in the search term of your browser, to find suppliers of the part that suit you best.