An older iPad cannot connect to the App Store message "cannot connect to app store"

It is possible that your WiFi router is unexpectedly blocking access to some internet/server resources - which might be resolved by a restart of your router.

To restart you home router, disconnect power - then wait at least 30 seconds before restarting. When you router has rebooted (which may take several minutes), force-restart your iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

It is also possible that your currently selected DNS servers(s) are not resolving, or a blocking, some resource addresses. Changing your DNS Server IP Addresses might resolve this problem.

For recommended DNS servers (configured at your home router and/or your iPad), you might choose one of the following Recursive DNS Providers (IPv4 and IPv6 addresses included below). Where your local network is dual-stack, you should enter both the IPv4 and IPv6 redundant server addresses.

Quad9

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare+APNIC

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001