iPhone 7 Plus not recognizing unlock code. Will not start

All that you can do is continue to enter the code. After 10 unsuccessful tries, the iPhone screen will display Unavailable. Then, you can reset the phone and set it up again with a new passcode, and use your backup to restore data back to the phone.

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

If you need more help, please contact Apple Support.

Support

So, does the message say "Unavailable" on the iPhone's screen?

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

Otherwise, if the screen does not display "Unavailable", what is the message that appears?

As I said, all that you can do is keep trying. When you have reached the limit of unsuccessful tries, the screen will simply display Unavailable and there will be no more tries.

That is when you need to connect the iPhone to a computer to reset the phone. The instructions are provided in the link that I already posted above.

Do you have a friend with a computer?