phone will not wake up from a black screen

There are two possible results when you run the Forced Restart detailed in the Apple Support document just above your name.

1) The phone will start working again

2) The phone has a hardware problem and will need to be serviced by Apple or an authorized Apple repair shop

If you have tried all the steps in the link above your post and they did not resolve the problem, then scroll to the bottom where it shows how to contact Apple Support directly.