If the phone is rooted, updating could brick it, so the update program first checks 2 things - is this the stock ROM and has it ever been rooted? If the first is no, or the second is yes, the rooting program "fails" - just as it's supposed to.
If it's never been rooted (even if you unroot it, updating isn't safe) and you're in the US, bring the phone into a Best Buy, go to the cellphone area and look for the Samsung rep (light blue polo shirt with a Samsung logo). Ask if s/he could please update your phone, because the update keeps failing.
06-25-2015 06:39 PM