My Dekunu does not turn on

I haven’t use my dekunu for a while, I try to turn it on but it doesn’t show that is charging

There is no indication that the is charging while the dekunu is off. Try leaving it on charge for an hour, then try turning it on, you need to hold the power button in for a second or two.
If that does not work try resetting it, there is a small hole near the plug and buying is, you will need a small paper clip. Hold the reset button in for a few seconds. Make sure the power cable is unplugged while you do this.
They are the only tips I know, good luck.