You may want to check the event viewer if there are any errors logged there.
Are you allowed or is it feasible for you to do code changes? 'coz you can implement tracing here. It's included in the documentation - Key Scenarios -> Tracing Activities and Propagating Context Information. Tracing can be easily enabled
and disabled in the config by selecting the Logging Application Block node and setting the TracingEnabled property to true/false. The quickstart also includes a walkthrough on this.
Or if you simply want to know what was the exception which causes your main window not to show up, put exception handling codes in places where you're suspecting the error occurred. Make sure the exception policy you use logs the exception it catches.
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