There have been several changes to macOS Sequoia's network stack. VPN might need to be turned off and back on if you have a VPN configuration profile. Or you might need to upgrade your VPN 3rd party software.
Limit IP Tracking needs to be turned on for WiFi if you are using Private Relay in iCloud. Try disabling Private Relay to see if things are working. I found that I had to turn on Limit IP Tracking after the upgrade because it was turned off. See if there are any indicators for iCloud Private Relay when going to your iCloud screen in Settings. In my case, it was telling me to enable Limit IP Tracking for things to work.
Or you can try turning off Limit IP Tracking as well as Private Relay and see if you can reach that website.
Check your DNS settings under WiFi Details -> DNS and try adding a couple entries for Google's public DNS servers.
Primary 8.8.8.8
Secondary 8.8.4.4