how to repair IBM T40?

I used my IBM T40 laptop but instead of closing down fully I just closed the lid. I only remembered I did this 3-4 days later and the computer would not restart despite pressing the "power" button for several seconds or removing and re-inserting the battery and trying to restart. In trying to charge the laptop the battery charger failed to warm up indicating it was not charging although when checked separately the charger was providing power correctly. I fitted another battery without any success.
Has anybody any idea what has gone wrong please?