My iPhone 7 Plus will not update

1. What version of iOS are you currently on?
2. Do you have a good WiFi connection?
3. If you are using a VPN turn if off.
4. Do you have 6GB of free space.
5. Make sure you have a 50% battery charge and preferably you are on the charger.
6. Turn off Low Power mode.

How long has it been on Update Requested. And do you have 6GB of free space.

If it has been like that for more than 30 minutes restart your iPhone and your router and start over.

Are you saying you are currently at 15.4.1? Settings > General > About > Version.

Do you meet everything in 2 - 6? What happens when you try to update?

Take a screen shot and post it here.