Are you sure the mainpower unit is functioning?
Also a possible checkh with those that know how the computer is powered?
Think -converted mains power to battery/ battery to computer and/or converted mains power to computer.
which happens do you think? - Will the computer run with out battery only through mains- in which case it may be a switching defect in the computer.
Run some checks so that you have a clear idea what could be possbily wrong before sending to a repairer- whuich you may wind up doing.