iphone 7 plus will not go into recovery mode

If you can't use recovery mode as described in If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support then see the following from the Get More Help section of that same link:

If you can't update or restore your device using recovery mode, or you can't use recovery mode because of broken or stuck buttons, contact Apple Support. Then follow the steps to set up service for your iPhone, iPad, or iPod touch.