2. Reset Sync History

Resetting your Sync History is a simple step which may resolve some syncing issues. If this works, iTunes will prompt to Merge or Replace the information on your device when you next attempt to sync. To reset your Sync History:

1. Disconnect your device.
2. Open iTunes.
3. From the Edit menu, choose Preferences.
4. Click the Devices tab.
5. Click the Reset Sync History button, and then reconnect your device.

If this resolves the issue, and you know all of your contacts, calendars, bookmarks and notes are on your computer:

1. Reset the Sync History again using the steps above.
2. Select the device in iTunes and click the Info tab.
3. Scroll down to the Advanced section, and under "Replace information on this iPhone/iPad/iPod touch" select Contacts or Calendars.
4. Click Apply.

If the issue persists, and you know all your contacts, calendars, bookmarks and notes are on your iPhone, iPad, or iPod touch:

1. Remove all of the contact and calendar information from Outlook.
2. Select the device in iTunes and click the Info tab.
3. Scroll down to the Advanced section, and under "Replace information on this iPhone/iPad/iPod touch" make sure Contacts and Calendars are not selected.
4. Click Apply.

Security updates are usually incorporated into later Software Updates

Security updates released for Mac OS X are usually incorporated into the next OS X Software Update.

Security updates may also be available for software released independently from OS X. Software Updates are packaged in a manner to keep systems secure. Security updates are only offered to systems that need the update, and not to later versions that have incorporated the Security Update. For more information, see the "Some, but not all, updates are displayed" section of this document. 

When you add UnionPay as a payment method in the App Store, you are required to provide the mobile phone number your card's issuing bank has on file for you.

If you experience issues adding your UnionPay card, try contacting your bank:

1. To add or update your mobile number associated with the UnionPay card.
2. To confirm that the card number is enabled for online purchases.

Some cards do not have mobile numbers associated with them. If this is the case with your card, contact your bank to update or replace it.

User-specific issues

If the issue only happens in one particular user account:

Create a new iTunes library to see if the issue occurs in a new library. If using a new iTunes library resolves the issue, recreate your old library in your new one.
To change back to your original library, close iTunes, and then hold down the Shift key on your keyboard while you reopen the program.

If the issue persists:

Check for issues with content files. Audio files can sometimes cause iTunes to quit unexpectedly or stop responding when the program is analyzing gapless playback information. To determine which file might be causing the issue, follow the steps below:

1. Quit iTunes.
2. Navigate to the iTunes folder:
   Windows Vista: C:\users\username\Music\iTunes
   Windows 7 and Windows 8: C:\users\username\My Music\iTunes
3. Move the iTunes Library.itl file to your desktop.
4. Open iTunes. Your library will be empty.
5. Press the Control and B keys on your keyboard to open the iTunes menu bar. Choose File > Add Folder to Library.
6. Navigate to the folder where your music is located:
   Windows Vista: C:\users\username\Music\iTunes\iTunes Media
   Windows 7 and Windows 8: C:\users\username\My Music\iTunes\iTunes Media
7. Choose an artist, album, or song to add to the library and drag it into the iTunes window.
8. Wait for iTunes to successfully add the item to your library and perform the gapless playback scan.
9. If the scan is successful, continue adding songs to your library.
10. If there's an issue with one of your files, your issue will reappear after you add it to the library. If it reappears, start over with these steps, being careful not to add the files that caused the issue.

Browse and buy

Tap App Store on your iPhone, iPad, or iPod Touch to browse and buy apps on your iOS device.

To browse the App Store on your computer:

• Open iTunes.
• Click iTunes Store.
• Click the More icon (three dots) in the upper-left hand corner of the window.
• Click Apps.

To buy apps, you need an Apple ID. If you don't have one, you can create an Apple ID in iTunes, or on your iPhone, iPad, or iPod touch. Learn what forms of payment you can use to buy apps and other content.

Apps you download in the App Store appear in your iTunes library, but you won't be able to use them on your computer. Use iTunes to sync apps with your device.

In-app purchases

Some apps offer additional purchases that you make within a paid application. Learn more about in app purchases. 

iOS devices

On most iOS devices, you can tap Settings > General > About to see your device's serial number, IMEI/MEID, and ICCID. If you're using iOS 6 or later, you can tap and hold on the number to use the copy option, then paste this information into Apple registration or support forms.

If you haven't yet set up your device, you can find the IMEI and ICCID by tapping the Info icon  on the lower-right corner of the iOS setup assistant "Hello" screen.

If you can't get to your About screen, use another option below based on the type of device you have. 

• iPad and iPod touch
• iPhone 5 and later, iPhone 5S, iPhone 5C, iPhone 6, and iPhone 6 Plus
• iPhone 3G, iPhone 3GS, iPhone 4 (GSM model), and iPhone 4s
• Original iPhone