This is due to using the Webview non-SSL port (8081) REST API not being enabled. Enabling the REST API resolves the problem.
1. Open the MOM_HOME/config/IntroscopeEnterpriseManager.properties.
2. Uncomment the following property
3. Enable the REST API by setting the following property.
4. Restart the EM.
Note: If using ETC (Enterprise Team Center) or ATC (APM Team Center), you will need to restart them as well.