Originally Posted by votinh
There was a report from a member with the exact same issue as you have, however, he said he did root and also delete one of the corresponding file, that was his problem, and soon after he move that file back into the system, QR worked as normal. Your case is kind of strange since you haven't rooted it yet.
My suggestion is factory reset.
Remember, you will lose everything, so backup first.
Done a LG Backup , transfered to my sister N4 and after factory reset made a reset of backup
It seems that it worked