Review the troubleshooting topic "Why can't I create a friendship between Rational ClearQuest and CLM applications, such as Rational Quality Manager, Rational Team Concert, and Rational Requirements Composer?" to make sure basic requirements for the integration are met.
Is the database missing from the list? See the above topic, item 5 for the query you can run to navigate to the registered data. You will need to investigate further with the ClearQuest administrator as to why it is not available for the connection.
Use a browser debugging tool such as Firebug to detect an errors or messages that may not show up in the UI. Typically, there is a response here to a call that will reveal more information on the failure which you can use to search for known issues.
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