Q: Can't update to 8.0.1 what happen?

Apple has pulled the iOS 8.0.1 update due to problems.

iOS 8.0.2 will be released in "the next few days".

Loss of cellular service or ability to use Touch ID after updating to iOS 8.0.1 on iPhone 6 or iPhone 6 Plus

We have a workaround for you if you have an iPhone 6 or iPhone 6 Plus and you lost cellular service and Touch ID functionality today after updating to iOS 8.0.1. You can reinstall iOS 8 through iTunes by following the instructions below. We are also preparing iOS 8.0.2 with a fix for the issue, and will release it as soon as it's ready in the next few days.

Your iPhone has had a notification to update for about five months now.  You're running iOS 7.1, but iOS 7.1.1 came out five months ago.

Use iTunes to update your iPhone to iOS 8.0, which is the current version, or wait for iOS 8.0.2 to come out.