unable to complete data transfer

Hello again,

I would especially like to point out that before you transfer data, you need to upgrade both devices to the current iOS version. Your iPhone 11 device is probably on iOS 14.4.1. However, your iPhone 12 device may be out of the box with iOS 14 version installed. You cannot transfer data from a new version to an old version. First, try to upgrade your iPhone 12 to iOS 14.4.1

If you are not using the latest version of iTunes, you may need to update it. https://www.microsoft.com/tr-tr/p/itunes/9pb2mz1zmb1s?cid=appledotcom&rtc=1

If you have a Mac OS Big Sur you can transfer data on Finder. https://support.apple.com/en-gb/HT210218

Regards,

Hello,

By putting both devices side by side, you can quickly transfer them.

You can view Apple Support's official video : https://www.youtube.com/watch?v=cpNk6fkwS2I

And you can look at this article too: https://support.apple.com/en-us/HT210216#:~:text=to%2Ddevice%20migration-,Turn%20on%20your%20new%20device%20and%20place%20it%20near%20your,to%20use%2C%20then%20tap%20Continue.

Regards,