If you can not update your iPhone 11 Pro or any other iPhone or iPad, make sure you follow the software update guideline listed below.
The phone must be charged to over 50%
Low Power Mode must be OFF
You cannot be connected through VPN
You must have a Wi-Fi connection (not cellular)
You should plug in the phone or put it to charge to assure it stays on and connected to Wi-Fi.
If you still can't install the latest version of iOS , try downloading the update again:
Go to Settings > General > [Device name] Storage.
Find the update in the list of apps.
Tap the update, then tap Delete Update.
Go to Settings > General > Software Update and download the latest update.
If you don’t see the update in the list of apps or if the issue happens again, you need to update your device with your computer using Finder or iTunes.
Why wont my iPhone 11 update?
Well, the reasone why your iPhone has refuse to update to the latest version is because of the following
Not enough available storage space on your device
Downloading the update takes a long time
Unable to reach the update server
The update doesn't complete