When reaching the Web service step in a workflow, you receive the following error, 

The activity Web service call failed with the following error message: "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel."

When experiencing this issue, please refer to the following recommendations;

  • Check whether the SSL Certificate has expired or is no longer valid. If this is the case, then the certificate will need to be renewed.
    This can be tested by entering the URL of your Web service in a browser, then see whether the Web Service comes up normally or if a page stating that the Web service is not trusted occurs. 
    If this page appears, it should say whether the certificate is expired and for how long it has expired.

  • Check the FireWall and AntiVirus from the server hosting the Web service.
    As a test, try temporarily disabling them to see if that clears up the issue. If it is resolved after this, then we know what the root cause of the issue is and can focus on what specifically is being blocked.
    For more on what should be exempt, please see KBA-36317.

  • Ensure TLS 1.2 is enabled.
  • Make sure the Web service is using the latest version of the API.

KBA is applicable for both Cloud and On-premise Organizations.