I can't turn on my Wi-Fi in iphone 4s?

I can't turn on my Wi-Fi in iphone 4s?

I would suggest you to perform a network reset but please note that all saved network will be gone after this. Go to settings general then reset and then click reset network settings hopefully this shall solve your problem.

If problem still persist then restore and update your phone.

I tried your suggestion but it didn't work on my unit