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Try plugging it in to the charger, and see if a light shows that it is charging.
Leave it on the charger for 6+ hours continuously. Does the light change to show it is charged? if so, don't take it off the charger, keep it on the charger for the full 6+ hours.
Then try it again.
If it doesn't work then, try putting it on the charger and turning it On there.
At which point, if all fails, examine the charger: does it look normal, no strain nor severe bending on the cords, no overheating?
Let me know what you find out, what happens - and, what the maker of the tablet is and what sort of charger it has, and how old it is. Thanks.