The following error is recorded in the Secure Gateway Event Viewer:
SSL Library Error 47 Event ID 127
Browser: 503 Service Unavailable

Complete the following steps to troubleshoot this issue:

1. Go to IIS > Application Pools > CitrixWebinterface2.4.0AppPool. Make sure that the:
   • Status is Started
   • .Net Framework version is v2.0 
2. Right-click on CitrixWebinterface2.4.0AppPool and choose Advanced Settings. In General section, make sure that Start Automatically is set to True.

3. Ensure that you are using the latest version of Secure Gateway.