why wont itunes work when i try to sync my iphone5s

Hi simous,

Welcome to the Support Communities! What do you mean by "iTunes stops working." Did you get an error message? What happens if you quit iTunes, restart your computer, and try again? Do you have the latest version of iTunes on your PC? Here is some information on the syncing process and troubleshooting steps.

Apple - iTunes - Download iTunes Now
http://www.apple.com/itunes/download/

iTunes 12 for Windows: Syncing overview
http://support.apple.com/kb/PH20342?viewlocale=en_US

iTunes 10.5 and later: Troubleshooting iTunes Wi-Fi syncing - Apple Support
http://support.apple.com/en-is/TS4062

iTunes 10.5 and later: Troubleshooting iTunes Wi-Fi syncing

With iTunes 10.5 and later, you can sync your iOS device over Wi-Fi. Try these steps if you see these symptoms:

• You can't view your iOS device in iTunes over your Wi-Fi network.
• You see issues with Wi-Fi sync performance.

Check the system requirements for Wi-Fi syncing

• An iOS device using iOS 5 or later on the same Wi-Fi network as your computer
• A computer using iTunes 10.5 or later and one of these operating systems:

• Windows XP, Windows Vista, Windows 7, or Windows 8
• The latest updates for your iOS device, iTunes, and operating system:

  To update an iOS device, follow these steps.

To update Windows, see Microsoft's Windows Update page.

Turn on Wi-Fi syncing

To sync your content to your iOS device through Wi-Fi, you must turn on the option in iTunes:

1. Connect your iOS device to your computer using the Apple USB cable.
2. Open iTunes and select your device on the left side of the iTunes window. In iTunes 11, your device will be in the upper-right. You can also find your device by expanding the sidebar from the View menu.
3. Click the Summary tab.

   

4. Scroll to the Options section and select "Sync with this [iOS device] over Wi-Fi."

   

5. Click Apply.

Quit and reopen iTunes and restart your iOS device

Quit and reopen iTunes on your computer. Then, restart your iOS device.

Restart your network router

Restart your home network router using the manufacturer's instructions. You may need to disconnect the power cord for 30 seconds or more.

Note: During this time, Internet services, such as a VoIP-based phone, won't work, and you may need to reset additional network devices.

Check your network connection

• Make sure that your Wi-Fi network has an active Internet connection.
• Make sure that you connect your iOS devices and computer to the same network over Wi-Fi.
• Check for network configuration changes that may interfere with syncing:
  
  • VPN configurations
  • Extending the Wi-Fi network through multiple wireless access points or routers
  • Guest networks or other security configurations that limit access between devices
  • Routers that configure different networks for different frequencies such as 2.4 GHz and 5.0 GHz
  • Connecting the computer over Ethernet
• Wake up your computer and open iTunes. If your computer is asleep or iTunes isn't open, the device may not sync.
• Update your router. If you're using an AirPort or AirPort Time Capsule, you can learn more about firmware updates. If you're using a router from another manufacturer, contact the manufacturer to ask about available updates.

Check for network interference

If you see performance issues when you sync over Wi-Fi, something may be causing wireless interference:

• Microwave ovens
• Cordless phones
• Physical barriers, such as metal walls or distance between your computer, base station, and iOS device

Try the following to reduce network interference:

1. Move your iOS device and computer closer to the Wi-Fi router or base station.
2. Check for sources of potential interference.
3. Remove your iOS device from any case, stand, or attachment.
4. Open Safari and try to load a webpage.

Check firewall settings

If you enabled a firewall on your router or computer, make sure that your computer and iOS device can communicate.

• Follow these steps to use the built-in firewall option with iTunes on your Mac.
• For third-party firewalls and security software, see the developer or manufacturer for assistance.

Mac computers use port 123 to set the date and time automatically. Incorrect date and time on a computer or iOS device can cause connection issues. If you don't know if your router has a firewall or if the required ports are open, follow these steps:

• Enable Wi-Fi syncing for additional iOS devices on your network to see if they have the same issue. (See the previous steps to enable Wi-Fi syncing for additional devices.)
• Test your device on a different network. If the device works on another network, the issue may be your router or network configuration. Contact your router manufacturer or Internet service provider for additional troubleshooting.

If you use another security or firewall software on your computer or router, you can troubleshoot security software issues, contact the manufacturer, or check the documentation to learn how to open TCP ports 123 and 3689 as well as UDP ports 123 and 5353.

Important: Mention of third-party websites and products is for informational purposes only and constitutes neither an endorsement nor a recommendation. Apple assumes no responsibility with regard to the selection, performance or use of information or products found at third-party websites. Apple provides this only as a convenience to our users. Apple has not tested the information found on these sites and makes no representations regarding its accuracy or reliability. There are risks inherent in the use of any information or products found on the Internet, and Apple assumes no responsibility in this regard. Please understand that a third-party site is independent from Apple and that Apple has no control over the content on that website. Please contact the vendor for additional information.

Last Modified: Aug 21, 2014

I hope this information helps ....

- Judy