Since iOS 7, connecting an iPhone, iPad, or iPod Touch to a computer generates a prompt to trust the PC before the connection can be established. The prompt message appears on the iPhone, iPad or iPod Touch and is designed to prevent unauthorized computers to access your device’s data.
This is how to unlock the iPhone and trust the PC
If you have enabled a passcode lock on your iPhone or if you are connecting the iPhone to your PC for the first time, the below message will appear in the CopyTrans program window
Unlock the iPhone. To do so, slide your finger from left to right over the “slide to unlock” screen. Next, enter the passcode
Once inside the iPhone, trust the PC. Simply tap “Trust” once you see the “Trust This Computer” prompt
Done! Your CopyTrans program now recognizes the iOS device and its content will automatically start loading.
If you accidentally tapped “Don’t Trust”, you’ll get the Trust alert each time you connect the device to the PC. If the Trust alert doesn’t display, restart your PC and re-connect the device. If you are running iOS 8 and the Trust alert still doesn’t appear, navigate to Settings > General > Reset > Reset Network Settings, then re-connect the device.