Why can't I connect my iPhone 4 to wifii?

I think it's most likely due to my iPhone 4 being upgraded to iOS 6.1.3.
My phone was able to connect when it was upgraded, but after 2 days I was unable to connect anymore.
It's like this, when I go into Settings then Wi-Fi, and go into it to on the Wi-Fi, it just wouldn't on.
All help would be appreciated.

Try restoring the software from itunes… I know it is irritating but you'll have to do it…
Let me know if you have any probs: p

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