Why is my phone not turning on?

My Samsung Galaxy S6 Edge is the phone that I use for almost one and a half a year now. I took it with me to school and in the last lesson, something happened which I don't know what that was. It went out as usual or more like sleeping mode. Now I can't get it back on. In my knowledge, it hasn't been in contact with water and it was charged when I went to school. I have tried to hold the power button, the home button and both of them at the same time, but it didn't help. I have never had this issue with this phone before. Please could anyone help?