@yashkumar3303 this battery may be discharged below it's charging threshold. Sometimes (if it is not to old) you can "wake it up" by using something like a 9V battery. Connect the Positive to Positive and then the Negative to Negative. Leave it connected for something like 5-10 minutes. Then reconnect your battery and see if your tablet will charge again.
If not, then it might be time to replace it. Since iFixit does not yet have a specific guide for that, use the [document|42062] for that. Page 52 of the manual deals with the battery.
While you work on your tablet, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!