Q: itunes not connecting my i6s.

What is the version of OS X on your Mac? You should update to OS X compatible with the latest iTunes version.

https://support.apple.com/en-us/HT201377

You have not provided much background information for us to provide a simple, clear answer.  See: Writing an effective Apple Support Communities question - https://discussions.apple.com/docs/DOC-5931

Go to the upper left window of your computer and under the Apple select Software Update.  If it says you are up to date:

iOS9 on a mobile device requires iTunes 12.3 or higher which in turn requires a computer running OSX 10.8.5 or higher.  System Update only checks for updates for the current system version you are running but that itself may be out of date.  It may or may not be possible to upgrade your computer to the required system:

You can either buy a download code for OSX 10.8 Mountain Lion from Apple online, or you can try installing the free El Capitan OSX 10.11.  El Capitan may run slower on older machines and require additional RAM purchase.  Doing a big jump in system versions is also more likely to affect old software.

Snow leopard to el capitan, will it cause my macbook to be slow?  - https://discussions.apple.com/thread/7412959

Mountain Lion 10.8 purchase link U.S.A. - http://www.apple.com/shop/product/D6377Z/A/os-x-mountain-lion

Mountain Lion 10.8 purchase link U.K. - http://www.apple.com/uk/shop/product/D6377ZM/A/os-x-mountain-lion

Current OSX general upgrade information, including system requirements - http://www.apple.com/osx/how-to-upgrade/

If you have any PPC generation software that has been running under OSX 10.6 it will not be supported under any later system versions.