This happens if there is no database passed to the icon by the Notes client or Designer.
In the Notes client, open the database before clicking on the tool icon.
In Designer, the focus of what the current database is may be lost by a number of actions (eg using the XPages perspective). Using a right click in the Application panel on the database or a specific element, then selecting Configurator from the context menu may force Designer to regain focus on the database.
Alternatively, opening an element, then immediately pressing the Configurator icon may also force Designer to regain focus on the database and pass it to the icon.