Hello there, Tom.
Thanks for reaching out to us here on the Apple Support Communities.
When confronting connection issues with iTunes on your Mac the following Knowledge Base article provides a great place start:
Can't connect to the iTunes Store - Apple Support
Since you've already verified versions, feel free to review the following:
If you haven't been able to connect to the iTunes Store, a software conflict or your Internet service provider (ISP) may be blocking your access.
- Update iTunes and Safari to the latest version.
- If you have a firewall, your settings may be preventing you from connecting to the iTunes Store. Follow these steps to configure your firewall.
- You may need to reset your keychain. Connection issues are occasionally caused by keychain issues. Learn how to use Keychain First Aid to resolve any issues with your keychain.
- If you're receiving a specific error message, follow these steps.
- If the issue still persists, contact your Internet service provider and confirm that these ports and serversare enabled over your network.
If you find the issue persists, then this article delves into some Advance Troubleshooting recommendations:
iTunes: Advanced iTunes Store troubleshooting - Apple Support
Cheers,
Pedro.