hello
if the keys are flashing on each second when the tablet is connected to a power source, the tablet is in a state called flashing mode

You need to let the tablet to charge for several hours, and then press the power key for more then 30 seconds while is connected to a power source, if you don`t get any results, try without the power source, again, more than 30 seconds.

If it works, feel free to donate, because I just saved your tablet from being a brick.