Check that your Windows and iPhone are running the most recent iOS version. If you're using iTunes, check sure you're using the most recent version. Restart your iPhone and computer. Connect your iPhone to your computer using the original Apple USB connection, then try a different USB port. On Windows, make sure Bluetooth is disabled before trying another USB port.
Check to see if your iOS or iPadOS device is unlocked and on the home screen. Check that your Mac or Windows PC is running the most up-to-date software. Check to see if your device is turned on. Unlock your smartphone and hit "Trust this Computer" if you receive a "Trust this Computer" notice. Unplug all USB devices.
Check that your iOS or iPadOS device is on, unlocked, and on the home screen. Start your iPhone, iPad, or iPod touch again. Then, click the menu icon (3 horizontal lines) in the top-right corner of the iTunes window, then select Preferences. Under Devices, make sure your phone is selected.
If your USB cord and port are completely functional, the next step is to install the most recent iTunes version to resolve the "iTunes cannot backup iPhone" error. When you connect your device to the computer, iTunes will run immediately. To open it, you may need to double-click it. If you get an error message that reads "Cannot connect iPad to iLife iTunes 9.0.1", click the OK button to close this window and try again.
If you're running a newer version of iTunes than 9.0.1, make sure that your computer has the latest driver updates for your device installed. You can check here if there are any available: http://support.apple.com/kb/HT543
If you still can't figure out what's wrong, call Apple Support at 1-866-220-8344. They should be able to help you over the phone.
If you attach your device to your computer through a USB cable and iTunes fails to identify your iPhone, iPad, or iPod, seek assistance. When iTunes on your computer fails to identify your connected device, an unknown error or a "0xE" error may appear. In this case, contact Apple Support.
If your iPhone is still not showing up in iTunes, make sure everything is absolutely up to date. If feasible, update your iPhone, iTunes, and your computer's operating system (whether MacOS or Windows). To update iTunes on a Windows PC, launch iTunes and navigate to Help > Check for Updates. The latest version of iTunes automatically checks for updates and will notify you when there are new versions available.
If you are attempting to sync your iOS device with iTunes on a Windows PC, you must first update the device's drivers. Navigate to your PC's Device Manager and right-click your iOS device. You can afterwards restart iTunes and reconnect your device to see whether the sync session fails to commence.
The reason is that iPhone images cannot be seen on a PC. It might be due to a faulty USB cord. The camera roll folder on your iPhone may be empty. The USB port on your PC may not operate properly or may just malfunction. A missing or corrupted iPhone driver may prevent the device from being effectively detected by the PC. Try to connect your iPhone to the computer using a different USB cable or plug its dock connector into a powered USB port on the computer.