When you are sure the battery is fully charged I don't think there is much you can do. Lots of things, like a bad charger, a bad cable, bad connectors and a bad battery, can be the cause the tablet does not have enough power. But when there is enough power, the on / off switch cam be defect, or any electronic part in the tablet could be. Without the tablet i my hands and measurement tools to verify everything it will be impossible to tell what is wrong. Take it to a repair centre, but before you leave it, ask what they charge for the diagnose. Not sure you can swap the battery and how difficult it would be to get one? Perhaps that is the problem, but don't take my word for it.
Answers & Comments
When you are sure the battery is fully charged I don't think there is much you can do.
Lots of things, like a bad charger, a bad cable, bad connectors and a bad battery, can be the cause the tablet does not have enough power. But when there is enough power, the on / off switch cam be defect, or any electronic part in the tablet could be. Without the tablet i my hands and measurement tools to verify everything it will be impossible to tell what is wrong. Take it to a repair centre, but before you leave it, ask what they charge for the diagnose. Not sure you can swap the battery and how difficult it would be to get one?
Perhaps that is the problem, but don't take my word for it.