I keep getting a "cannot open the page because it could not connect to the server" message when I scan the QR codes

The most likely reason for this error is due to the firewall. 

Please switch off your WiFi and try via phone data and see if you can access it. 

If you still face the issue, please refer to this article for the steps to prevent this: https://itoolab.com/fix/how-to-fix-safari-cannot-connect-to-server/