Why did my application utilizing SOAP or REST API break when a virtual host was implemented?
Connect REST, Connect Web Services for SOAP, Knowledge Foundation APIs
When a virtual host (otherwise called "vhost" or "custom domain") is implemented on a site interface, this will change the web service endpoint configuration used to connect using the Connect REST API, Connect Web Services for SOAP (CWS) API or Knowledge Foundation (KF) API on that interface. The domain within the endpoint configuration will need to reflect the primary virtual host configured and any customizations/integrations using the previous domain's endpoint configuration will break if not modified to reflect the new domain.
For further information on the implications of alternate vhosts on the SOAP API endpoint configuration, refer to Answer ID 8117: SOAP and REST APIs only accessible via the interface's primary virtual host.
For further information on appropriate formatting of SOAP API endpoint configurations, refer to Answer ID 6741: Correct Syntax for connecting through the wsdl.
For information on troubleshooting SOAP API endpoint configurations, refer to Answer ID 6756: Access Denied with SOAP API .