Can't get wifi on iPhone 4s since updating to ios8

Hello burnxburn,

If you still haven't been able to connect to a Wi-Fi network after updating to iOS 8.1.3, I would use the troubleshooting in the following article, named:

If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network

Thank you for using Apple Support Communities.

All the very best,

Sterling

Ah ok, thank you for the clarification. Instead I would have you do the steps in this article, rather than the first one.

iOS: Wi-Fi settings grayed out or dim

1. Restart your iOS device.
2. Make sure that airplane mode is off by tapping Settings > Airplane Mode.
3. Reset the network settings by tapping Settings > General > Reset > Reset Network Settings.
   This will reset all network settings, including Bluetooth pairing records, Wi-Fi passwords, VPN, and APN settings.
4. Make sure that your device is using the latest software. To do so, connect your device to your computer and check for updates in iTunes.

If you still can't turn Wi-Fi on, please contact Apple for support and service options.

This is a Hardware issue, my iPhone4S wifi greyed out when iOS7 was upgraded on my phone... So i ended up replacing my Wifi Chip (Wifi iC) and its been working till then and also I successfully updated to IOS8 without it being greyed out... I do how ever recommend that u should try leaving ur iPhone off for 15-25mins with Airplane mode and Do not disturb mode on.. Then try to see if wifi is up and running... If no then u want to check to see if u need to get ur wifi ic replaced because the Wifi chip may be really hot that in order to get it running it needs replacing.. If u go to Settings>General>About and scroll to find Wifi Address if u see N/A that means u need to replace ur wifi chip, if u see numbers n letters then go to YouTube and find a temporary fix which is using a hair dryer..

Hope this Helps? :')

Since the issue persists after you performed the troubleshooting in my previous article you will need to obtain service for your phone:

iPhone Repair and Service - Apple Support