Here are a variety of resources (yes, I know you have crossed off some of them) helping with connectivity issues:
Restart your equipment and/or sign out and back in again, and try again.
If you can't connect to the App Store, iTunes Store, or other Apple services, read this support article --> If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support
Here's a related article about what to do if you can't connect or sign in to iCloud --> If you can't connect or sign in to iCloud - Apple Support
If your iPhone or iPad won’t connect to a Wi-Fi network, or if you have related connectivity issues, read this support article --> If your iPhone or iPad won't connect to a Wi-Fi network - Apple Support
Here's a case where using a VPN prevented sign-in --> AppStore - Apple Community
If none of the resources provide a solution, contact Apple for assistance:
For support, click here --> Choose your country or region - Official Apple Support Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world."
Click here --> Contact Apple Support - Apple Support
