I phone 7 not update in phone new version

see these

Update phone

Click on this link

Update your iPhone, iPad, or iPod touch - Apple Support

Phone will not update

If your iPhone, iPad or iPod touch won’t update - Apple Support

User Tip updating iOS

 Updating iOS: common issues and solutions - Apple Community

If you still can't install the latest version of iOS or iPadOS, try downloading the update again: Go to Settings > General > [Device name] Storage. ... Tap the update, then tap Delete Update. Go to Settings > General > Software Update and download the latest update.

That is one of many possibilities but we don't have sufficient detail to know where the process failed.