If you're having trouble with an Android device or iPhone, see the below notes:
On Android devices: You might need to change the USB setting to allow you to transfer media or photos and not just charge the phone. Go to Notification Center and choose Transfer files or File transfer. If your photos or videos are stored in the cloud, you won’t be able to download them, since they then exist in the cloud and not on your device. If you want to import your photos or videos to your PC, download them from Google Photos in your browser or use the Your Phone app from Microsoft Store.
On iPhones: Make sure your phone is unlocked, and when you see the Trust this device notification, select Accept. If iCloud is enabled on your iOS device, you won’t be able to download your photos or videos, since they then exist on iCloud and not on your device. If you want to import your photos or videos to your PC, do so via the iCloud desktop app.
If you’re having trouble with your Apple ID, passcode, or Apple verification code, go to Apple Support for more info.