My WiFi is not working

Apple’s only solution is to replace the phone. But as your 6S is 7 years old I don’t think it’s worth the investment to have Apple “repair” it by replacing it. Here is the process and cost→Apple - Support - Service Answer Center.

dami ~ What model of iPhone is it?...

Settings > General > About > Model Name

What version of iOS is it running?...

Settings > General > About > Software Version

õ¿õ¬

dami183 wrote: "It’s iPhone 6s the iOS version is 14.0.1 (18A393)"

dami ~ Does your iPhone 6s still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

õ¿õ¬

dami183 wrote: "yes it’s the original battery and it’s capacity is 100%"

dami ~ That doesn't make sense. The original battery of an iPhone 6s will be 3½–6½ years old — so it's very unlikely that such an old battery's capacity is actually 100%.

Did you purchase the iPhone 6s new or used?

When did you purchase it?

õ¿õ¬

Alancito wrote:

dami183 wrote: "yes it’s the original battery and it’s capacity is 100%

"

dami ~ That doesn't make sense. The original battery of an iPhone 6s will be 3½–6½ years old — so it's very unlikely that such an old battery's capacity is actually 100%.

It can make sense; the battery condition gauge in older devices was really pretty flakey and would frequently read 100% forever. If you have a Mac you can get the free app Coconut Battery, which will give a better indication of the state of the battery, including cycle count. There’s also a diagnostic file that shows cycle count. And if the battery was ever replaced with a non-Apple battery the gauge is completely useless.

The more important thing in Battery Health is what it says about Peak Performance Capability.

That usually indicates failure of the radio chip that manages both Wi-Fi and Bluetooth - especially if you can’t turn on Bluetooth, either. It’s time to replace the phone.