My iPhone 6 is failing to update iOS 14.0 software to iOS 14.0 I don’t know why

The iPhone 6 is not compatible with iOS 13 or higher. It can be updated to iOS 12.5.7, no further.

What is the existing version of iOS?

Alfredo643 wrote:

So how comes mine has to failed to update

Can we assume you have already solved your tech support issue by merely posting the text above? If so, well done.

What is you current version, is should be 12.5.7? That is all you can get. Verify the version in Settings.