I cannot update iPhone 5c from seed release to GA iOS 8

Currently have Build Version 12A4297e installed

When I try to update from iTunes I get the message that " This versions of the iPhone software (8.0) is the current version"

When I download the iOS and attempt to manually update (using ALT-Restore with the restore image iPhone5,3_8.1_12B411_Restore.ipsw) I get the message The iPhone could not be restored because the firmware file is not compatible.

What can I do to force or enable an update to the current latest released version?

I have reset the device and wiped it clean multiple times, it has never been jailbroken or in any other way tampered with.