403 forbidden

So multiple different devices all get the HTTP 403 forbidden error?

Check that your DNS is correct, or switch to 1.1.1.1, or to 8.8.4.4 and 8.8.8.8, or to 9.9.9.9 as your DNS provider.

If you have a network filter or content filter on your firewall, disable it.

If you have a VPN client installed, disable and re-test.

If you have add-on anti-malware or add-on anti-virus apps around, disable and re-test.

Check access to the support site using the cellular network. Bypass the Wi-Fi path.

Switch your DNS to a different provider, as a test.

Are you using a VPN to tunnel into a different iTunes Store? Have you tried with Safari or the Apple Support app?

What country are you located in?