To resolve this error, begin completing the following steps until the error clears.
  1. ​Ensure the application pool is started.
  2. Confirm port 443 and port 80 are open for incoming and outgoing traffic on your firewall
  3. Restart IIS
  4. Restart the server
  5. Ensure the domain being used for The Raiser's Edge Web Service URL is still valid and can be reached externally

If issue is still unresolved, Click Chat with Support and reference this article.