Q: I cannot sync my iPhone 6.  Error message: "Unknown error (-50)".

Hey there Mountain AERIE,

It sounds like you're just trying to update the content on your phone with iTunes but you keep getting this error code. I would use the troubleshooting in the following article to help fix this, named:

iTunes: Resolve USB-related alerts

 

Try these steps to check the connection between your device or computer. You might need to do only one of these steps to resolve the issue, so test your connection after each step.

1. See if the cable connection at the device or computer has come loose or unplugged.
   Unplug the cable you're using to connect your iOS device from the USB port on your computer, and then reconnect it. Then unplug it from your iOS device, and reconnect it.
2. Remove any third-party battery packs or cases from the device and ensure that the USB cable is connected directly to the port on the device.
3. If your Lightning or 30-pin cable is connected to a keyboard, display or USB hub, try plugging it directly into a USB port on the computer instead. 
4. Close any virtualization apps (such as Parallels or VMWare).
   These apps may interfere with your computer's ability to communicate over USB if they aren't properly configured, or up to date. If this resolves the issue, contact the developer of the app to see if an update is available.
5. Restart your computer.
6. Restart your iPhone, iPad, or iPod touch.
7. If your iOS device displays the Connect to iTunes screen, reset your device and then restore it.
8. If you're using an accessory or third-party cable to connect your device, try using an Apple cable with the device instead.
9. Update to the latest version of iTunes if you haven't already.
10. Disconnect other USB devices from your computer, except for your keyboard and mouse. Then, reconnect your iOS device. If the issue is resolved, reconnect the other USB devices one at a time. Make sure your iOS device is still recognized by the computer after adding back each device. 

If one of these steps resolves the issue, but it comes back later, make sure you haven't changed how the device is connected. For example, check to see if you plugged the device into a specific accessory, or used a specific cable that reintroduced the issue.

Thank you for using Apple Support Communities.

All the very best,

Sterling