you are not rooted and not running a custom kernel?
check your csc by dialing
*#272*your imei here#
your emei you can find by dialing *#06#
your cscs should be the same as rom.
change will wipe your phone so backup all you want to keep.
Change csc and try again.
root, backup efs to computer
dont know code to get pcode on JB.
which is why we go back to gb.
In recovery flash Phillz kernel, in his thread first post explained how.
Take out external sd card.
bootback into recovery
choose factory reset
wipe dalvik somewhere in menu advanced I think
go to mounts
format all, you took out external so you get error at one which you can ignore.
this is clean downgrade to gb
go to download mode and flash via pcodin (seek drdketans guide) the gb rom with csc you want.
After check your csc again.
then check pcode by dialing *2767*4387264636#
its the code which starts with n7000
that should match your rom. If it doesnt not sure if it will work. It never did for me via Kies.
Anyway if that, imei and csc aligned and not root or custom kernel, not unbloated(removed stock apps) then I was able to update via Kies.
Sometimes I just need to delete kies and every reference in registry to make it work.
I suggest before you try all above, except for backing up efs on off phone, to just pcodin your choice of firmware(either from drketans thread, or sammobile)
Because it just to much work lol.
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