
When you see the "A software update is required to connect to your iOS device. If you have no interest in updating your Mac to the newest macOS, the answer may be painfully obvious. How to Sync Your iPhone with iTunes Again

You will, however, still be able to charge your iPhone and use other tools such as Image Capture, Photos, etc. If your iPhone is running a newer version of iOS than the macOS version you're running currently supports, you will not be able to sync your iPhone with iTunes if you get the "software update is required to connect to your iPhone" alert.

Generally, if your Mac is running the latest macOS version and your iPhone is running the latest iOS version available, you should never see this message appear on your laptop or desktop's screen.

If you're currently running macOS 10.11 or higher on your Mac and connect your iPhone to sync with iTunes, you may get an alert saying that "a software update is required to connect to your iPhone." Here's everything you need to know about what that means, how to update your system, and what to do if updating doesn't work.
