Hello,
If your iPhone 7 won't turn on, the battery of your device may be drained completely. You can charge it for some time to see whether you can turn it on. If not, there may be some software or hardware issue on your device. You can try some third-party
iPhone iOS repair software [tuneskit.com] such as TunesKit iOS System Recovery for Mac. It's a powerful tool to fix various system issues without data loss, like iPhone stuck in recovery mode, white Apple logo, black screen of death, keep restarting, update failure, etc.
Read more details in this post:
How to Fix the Issue of iPhone Won't Turn on [tuneskit.com]