Can't install JB OTA update

[Alexd27]

Hi I have been looking online for my options and what might be wrong with my phone that would prevent me from being able to install the new update. I bought my phone from a guy who had it rooted and said he unrooted it before I got it. When I turn it back on it says Safestrap v3.07 is there but I don't see it on any of the apps. I don't have a clue what I'm doing or how to return it completely back to stock. I did a factory reset in the hopes that it would fix it but that seemed to be pointless. I need some help.