If you are unable to move past the firmware update after restarting, you may need to perform a factory reset. To do this, navigate to: Settings icon > Backup & reset > Factory data reset. It's extremely important to backup your data first before resetting your device entirely. This will restore it to the default settings when you first acquired it.
Afterwards, see if you are able to download the update. If you are still experiencing issues after the rest, please let us know. Thank you!
Collin, AT&T Community Specialist
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