Hi @sumy
First thing is to get the laptop starting and then once that's achieved is to look at the Windows problem.
Try the following:
Disconnect the charger from the laptop (if it is connected)
The ''press and hold the Power button operated for 20 seconds'' and then release it.
Try turning the laptop on.
If still no good, open the laptop and remove the battery from the laptop. Once it is removed ''press and hold the Power button operated for a full 30 seconds and then release it.''
Reinsert the battery, reassemble the laptop, connect the charger and then check if it turns on OK.
FYI Here's the [http://h10032.www1.hp.com/ctg/Manual/c06297488.pdf|maintenance and service guide], taken from this support [https://support.hp.com/au-en/product/setup-user-guides/hp-envy-15-cn1000-x360-convertible-pc/model/27691266|webpage] for your model.