# How old is the device or battery
# Without any load it may show 3.7V but with load it may fail.
# Connect battery to tablet - close device - start it - does it work for at least few minutes
# Do (3) then, connect to charger and the press powerbutton.
# Can you see the manufactured date in the battery? If it is more thant 3 years - may be better to get a new battery. Search eBay or aliexpress.
(Do not connect to charger without battery - some devices can brick)