Following is the current status of FOTA server.
After system version up on September 26th 2018, FOTA may become fail regarding state of terminal.
Data initialaization is required for following model (before Android 4.4).
Please confirm the following page for initialization procedure.
How to respond when an error is displayed during system update
For other models (Android 5.0 or later), please wait for about 1 week at longest and retry FOTA operation.