Hi, make sure the ac adapter is disconnected until later on in the steps. i recommend you open up the bottom part of the laptop and disconnect the battery from the board, then hold the power button for 30 seconds. then leave it disconnected for an Hour or just 30 minutes and then plug the ac adapter only while leaving the battery disconnected.   let me know how it goes.
There was an error message shows up before I started my laptop, but only once and I forgot the accurate content. Something like "the battery cannot be xxx".  Now I cannot see this anymore even though my battery is still not working. The battery is fully charged and kept in charge. But the laptop just shuts down if I take off the ac adaptor.     I have just updated my BIOS, so it should be OK. Should I replace the battery with a new one??? BTW, I have done the diagnostics online and passed all the hardware tests, everything is OK.
X15 R1. My battery is not working