Go to the "Options > Add-On Manager" Dialog and see if Lumion is listed.
Also, is the checkbox by its name checked? Because that means it is enabled.
If so, then go to the "Work Environment" Dialog, and in the "Menus" page, check in the list of available command and menus if there is any Lumion-related command you could add to your menu, using which to start the Lumion Connection.
Don't you have a PDF Guide for Lumion that details these things?
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