Ask Apple for Support
If nothing seems to be working, your iPad might need to get a new battery. You can try talking to Apple’s tech support and see if there’s any way they can help before changing the battery.
If there isn’t anything they can do, you can try asking for a battery replacement. There are ways for you to do it yourself, which could be cheaper, but only if you know what you’re doing. For the rest of us, talking to Apple would be the best option.