Often when you install the IdP into Tomcat and make some initial configuration changes, things just don't work. You might get a Tomcat error when you access the /shibboleth-idp/SSO location, or sometimes just a 404 page. You check your logs and nothing's there, and Tomcat's catalina.out file has nothing interesting in it.

Usually what happened is your configuration files are incorrect/invalid. The problem is that Tomcat eats all of the error messages Shibboleth outputs until later on in the startup process.

To properly diagnose the error, you'll need to look at the CreateUsefulContainerLogs topic. From that, you'll get more logging you can use to fix the error.