Considering what you've tried, I would suggest a factory reset. If that doesn't help, then it would need to be sent in for a formal repair.
I have the same problem. I was using the gear VR headset when my fine overheated then went off. Now there is no life what so ever! I have tried the reset suggestion but nothing. Where can I get the phone fixed please and what kind of price am I looking at.
Thank you for reaching out. To find your nearest authorized service center, you can use this link: https://www.ubreakifix.com/samsung We do not have pricing as this is determined by the repair center.