Help System update 4.0.2.a.0.62 fails

[mayura286]

I got the notification as above.but everything I try to update my Xperia ray phone it fails.
Tried to update through the phone.but the download finishes in a second and it says it is ready to be updated.
But when I try to update the phone restarts.and a message saying "update failed "appears.

Please someone help me.
Thanks.

 

[mayura286]

I got the answer.its to activate national roaming while downloading the update.