I keep getting a "Safari cannot open the page because the address is invalid" message when I scan the QR codes

Below are some of the fixes you may try to fix this error message on Safari:

• Check your internet connection: Power cycle your router. Then, try reconnecting to the Wi-Fi network and see if the problem disappears. If you are still facing the issue, you can switch to Cellular data.
• Restart your device
• Refresh the Safari page.
• Quit Safari and re-launch it.
• Disable desktop website mode: To do so, follow the below-mentioned steps:
  • Open Settings.
  • Next, choose the Safari option.
  • Now, select Request Desktop Website under the Settings for a Website section.
  • Toggle off the button next to All Websites.
• Clear Safari Cache files: To do so, follow the below-mentioned steps:
  • Open Settings.
  • Next, choose the Safari option.
  • After this, select Clear History and Website Data. 
• Change the DNS settings: If your DNS faces the issue, you might receive the Safari error message. In that case, you can add Google Public DNS and solve the problem. Refer to this article for steps to configure your network settings to use Google Public DNS - https://developers.google.com/speed/public-dns/docs/using