Q: my wifi is grayed out

Follow the steps on the article you linked from If Wi-Fi is grayed out or dim on your iPhone, iPad, or iPod touch - Apple Support including contacting Apple for service options.

Unfortunately the follow up when this does NOT work is the problem is hardware. This can't be the real answer. This is a programming thing. We upgrade to the latest iOS and bingo wifi disappears. Let's be HONEST please, APPLE people. Pl get us the fix and be fast about it. Thanks.

If those solutions (If Wi-Fi is grayed out or dim on your iPhone, iPad, or iPod touch - Apple Support) don't work your iPhone 4s has probably developed a hardware problem. The permanent solution is to get it replaced.

You can search the internet for heating and freezing solutions that might work (at least for a while).

For example, see here: https://www.youtube.com/watch?v=nj10bz5bI6A

Root cause: On some iPhone 4s devices there may be a flow soldering problem with the WiFi chip. After long periods of WiFi activity such as installing an iOS update (for example, iOS 8) there may be a connection failure. A work-around to this problem is the procedure in the youTube video.

A true hardware fix may be found here:

https://www.ifixit.com/Guide/How+to+Fix+iPhone+4S+Wi-Fi+Grayed+Out/22167

This happened to my wife's 4S back when I updated it to iOS 8. As user JimHdk points out, in all likelihood it points to a hardware problem due to excessive heat created by the update process. Nothing I tried worked...from hard resets to full resets, restoring from backups, etc. The wifi component more than likely has to be physically repaired or the phone has to be replaced. We chose the latter.