I had the same issue, pretty sure from not u rooting before the update. I tried everything, the priblem with my phone was that no apps installed so there was no launcher or browser or play store to install anything. I ended up taking it to T-Mobile and the useless girls took the back off put it back on and told me to return it. Long story short your prob gonna have to return it.
Also this goes without say but if your are rooted keep it to yourself if they ask any questions