Why is my App Store saying cannot connect

See the following Apple articles:

If you can't connect to the App Store, iTunes Store, or other Apple services

If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support

If you can't connect or sign in to iCloud

If you can't connect or sign in to iCloud - Apple Support

If your payment method is declined in the App Store or iTunes Store

If your payment method is declined in the App Store or iTunes Store - Apple Support

If you see a message that says "Your account has been disabled in the App Store and iTunes", contact Apple Support for help.

You need to update your payment information.

👉 Sign in to your Apple ID account page and edit your Apple ID details.

https://appleid.apple.com

On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.

Or -> Change, add or remove Apple ID payment methods

Change, add or remove Apple ID payment methods – Apple Support (UK)