Check your hosts file
After you update iTunes to the latest version, check the hosts file to make sure your computer can contact the update server.
Windows
If you’re using a Windows computer, follow the steps from the Microsoft support site. Resetting the hosts file affects software services that rely on hosts file redirects. If you're using Windows on a business computer, consult your IT department to be sure applications work correctly after you reset your hosts file.
Mac
If you're using a Mac, follow these steps:
1. In the Finder, choose Applications > Utilities.
2. Open Terminal.
3. Type this command and press Return: