A Mac can remain associated with a Wi-Fi network even when the network has no working internet connection. Check whether the issue affects only the Mac before changing advanced settings.
Test another device and website
Open more than one unrelated website, then test the same Wi-Fi from another phone or computer. If every device is affected, focus on the router or internet service.
Reconnect Wi-Fi and restart
Disconnect and reconnect to the network, then restart the Mac if the problem persists. These steps clear temporary connection states without changing custom configuration.
Check for VPN or filtering software
If the problem affects only the Mac, consider whether a VPN, security filter or recently installed networking utility is involved. Temporarily use the normal controls of trusted software rather than deleting system files manually.
Document custom settings before changes
If you use workplace, school or manually configured DNS/proxy settings, record them before resetting anything. That makes it easier to restore a required configuration.