Toshiba Battery wont charge, power adapter and battery both work ok

Hi there, my Toshiba Satellite Pro c850-1cw will not charge. The LED that illuminates when plugged into mains does not come on. The adapter works fine as it charges another laptop which is the same model. I have also tested it using a voltmeter and got 19vdc. I have bought a new battery which is also ok. I checked the 4 pins (2red,2black)at the connecter where the adapter goes in and they measure 19vdc also. Can anyone please direct me in finding what the issue could be and whether it will be potentially expensive. Thank you in advance.

Brendan