I installed iTunes v12.3.3.17 after which iTunes no longer recognized by iPhone 5S (software 9.2.1) or iPad2 (software 9.3). I searched various articles and instructions for a week and finally found one that worked for me. It was part of an old OSX Daily article for which I'll include a link at the bottom of my Reply, but the only step that worked for me (with the clarifications I've included below in caps, bold and underline) was the following instruction. I hope this will help someone else having the same problem. P.S. - I chatted online with Apple and also went the to Apple Retail Store before I found this article. Chat was no help at all as I had already done everything suggested by them and the suggestion at the retail store was that I bring in my 25" desktop with the iPad and iPhone so they could work on it.
For iPhone / iPad Not Being Detected in Windows, Update iPhone Driver
For Windows PC users whose iPhone, iPad, or iPod touch is not being found or detected by iTunes or the computer, you can update the iOS Device Driver like so:
- Go to the Device Manager in Windows, and locate “Apple iPhone” under portable devices section
- Right click on the ‘Apple iPhone’ and choose “Update DRIVER software”
- Now click “Browse MY COMPUTER FOR DRIVER SOFTWARE”
- Navigate to C:\Program Files\Common Files\Apple… and choose the folder called "MOBILE DEVICE SUPPORT" then “Drivers”
The updated driver will install and update and iTunes should now detect the iPhone, ipad, or iPod touch as intended.
That driver approach is for Windows PC, for Mac there is no driver to update in OS X aside from iTunes and general OS X system software, which is updated from Apple menu > App Store > Updates.
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Link to the entire article
http://osxdaily.com/2012/11/20/itunes-wont-detect-iphone-ipad-ipod/