این ارور به خاطر تنظیم نبودن ساعت توی سینک کردن رخ میده
مراحل زیر رو برو و تنظیمات ساعت رو درست کن.
Begin by quitting iTunes
Click the Apple menu at the top left-hand corner of the screen
Choose System Preferences
Click Date & Time icon in the System section (the 4th row)
Check the box next to "Set date and time automatically." This ensures that your computer's date and time are automatically set using an Internet-based date and time service provided by Apple
If your Mac's date and time are set correctly, close the System Preferences window and retry accessing the iTunes Store.
If it's still wrong, uncheck the box and manually set the date and time. Try to access iTunes again.