Apple News+ not loading on iMac with macOS Sequoia 15.5

On your Mac in System Settings, make sure you're signed into your Apple Account (your name at the top left), and confirm your subscription by clicking on your Apple Account > Media & Purchases > Subscriptions > Manage button. Do you see Apple News+ or Apple One on there?

What happens when you click News+ in the sidebar of the News app?

FYI, News+ works fine on my MacBook Pro on 15.5.

So it’s not News+ (as in the post title) but the Apple News app itself. That is a part of macOS. You may be able to delete the app and reinstall it from the App Store. Else you’ll need to reinstall macOS (use the option to preserve your data).

How to reinstall macOS - Apple Support

Do you mean that you can't launch the News application? Or do you mean that when you launch it, you can't see that you're subscribed to News+?